Microsoft007: INTRODUCTION To Oracle (SQl Queries)-II

ABSTRACT DATA TYPES

Some times you may want type which holds all types of data including numbers, chars and special characters something like this. You can not achieve this using pre-defined types.

You can define custom types which holds your desired data.

Ex:

Suppose in a table we have address column which holds hno and city information.

We will define a custom type which holds both numeric as well as char data.

CREATING ADT

SQL> create type addr as object(hno number(3),city varchar(10)); /

CREATING TABLE BASED ON ADT

SQL> create table student(no number(2),name varchar(2),address addr);

INSERTING DATA INTO ADT TABLES

SQL> insert into student values(1,'a',addr(111,'hyd'));

SQL> insert into student values(2,'b',addr(222,'bang'));

SQL> insert into student values(3,'c',addr(333,'delhi'));

SELECTING DATA FROM ADT TABLES

SQL> select * from student;

NO NAME ADDRESS(HNO, CITY)

--- ------- -------------------------

1 a ADDR(111, 'hyd')

2 b ADDR(222, 'bang')

3 c ADDR(333, 'delhi')

SQL> select no,name,s.address.hno,s.address.city from student s;

NO NAME ADDRESS.HNO ADDRESS.CITY

---- ------- ----------------- ----------------

1 a 111 hyd

2 b 222 bang

3 c 333 delhi

UPDATE WITH ADT TABLES

SQL> update student s set s.address.city = 'bombay' where s.address.hno = 333;

SQL> select no,name,s.address.hno,s.address.city from student s;

NO NAME ADDRESS.HNO ADDRESS.CITY

---- ------- ----------------- ----------------

1 a 111 hyd

2 b 222 bang

3 c 333 bombay

DELETE WITH ADT TABLES

SQL> delete student s where s.address.hno = 111;

SQL> select no,name,s.address.hno,s.address.city from student s;

NO NAME ADDRESS.HNO ADDRESS.CITY

---- ------- ----------------- ----------------

2 b 222 bang

3 c 333 bombay

DROPPING ADT

SQL> drop type addr;

OBJECT VIEWS WITH REFERENCES

To implement the objects and the ref constraints to the existing tables, what we can do? Simply drop the both tables and recreate with objects and ref constrains.

But you can achieve this with out dropping the tables and without losing the data by creating object views with references.

Ex:

a) Create the following tables

SQL> Create table student1(no number(2) primary key,name varchar(2),marks

number(3));

SQL> Create table student2(no number(2) primary key,hno number(3),city varchar(10),id

number(2),foreign Key(id) references student1(no));

b) Insert the records into both tables

SQL> insert into student1(1,’a’,100);

SQL> insert into student1(2,’b’,200);

SQL> insert into student2(11,111,’hyd’,1);

SQL> insert into student2(12,222,’bang’,2);

SQL> insert into student2(13,333,’bombay’,1);

c) Create the type

SQL> create or replace type stud as object(no number(2),name varchar(2),marks

number(3));/

d) Generating OIDs

SQL> Create or replace view student1_ov of stud with object identifier(or id) (no) as

Select * from Student1;

e) Generating references

SQL> Create or replace view student2_ov as select no,hno,city,make_ref(student1_ov,id)

id from Student2;

d) Query the following

SQL> select *from student1_ov;

SQL> select ref(s) from student1_ov s;

SQL> select values(s) from student1_ov;

SQ> select *from student2_ov;

SQL> select deref(s.id) from student2_ov s;

REF DEREF VALUE

REF

The ref function allows referencing of existing row objects.

Each of the row objects has an object id value assigned to it.

The object id assigned can be seen by using ref function.

DEREF

The deref function performs opposite action.

It takes a reference value of object id and returns the value of the row objects.

VALUE

Even though the primary table is object table, still it displays the rows in general format.

To display the entire structure of the object, this will be used.

Ex:

1) create vendot_adt type

SQL> Create type vendor_adt as object (vendor_code number(2), vendor_name

varchar(2), vendor_address varchar(10));/

2) create object tables vendors and vendors1

SQL> Create table vendors of vendor_adt;

SQL> Create table vendors1 of vendor_adt;

3) insert the data into object tables

SQL> insert into vendors values(1, ‘a’, ‘hyd’);

SQL> insert into vendors values(2, ‘b’, ‘bang’);

SQL> insert into vendors1 values(3, ‘c’, ‘delhi’);

SQL> insert into vendors1 values(4, ‘d’, ‘chennai’);

4) create another table orders which holds the vendor_adt type also.

SQL> Create table orders (order_no number(2), vendor_info ref vendor_adt);

SQL> Create table orders (order_no number(2), vendor_info ref vendor_adt with rowid);

5) insert the data into orders table

The vendor_info column in the following syntaxes will store object id of any table which

is referenced by vendor_adt object ( both vendors and vendors1).

SQL> insert into orders values(11,(select ref(v) from vendors v where vendor_code = 1));

SQL> insert into orders values(12,(select ref(v) from vendors v where vendor_code = 2));

SQL> insert into orders values(13,(select ref(v1) from vendors1 v1 where vendor_code =

1));

SQL> insert into orders values(14,(select ref(v1) from vendors1 v1 where vendor_code =

1));

6) To see the object ids of vendor table

SQL> Select ref(V) from vendors v;

7) If you see the vendor_info of orders it will show only the object ids not the values, to see

the values

SQL> Select deref(o.vendor_info) from orders o;

8) Even though the vendors table is object table it will not show the adt along with data, to

see the data along with the adt

SQL>Select * from vendors;

This will give the data without adt.

SQL>Select value(v) from vendors v;

This will give the columns data along wih the type.

REF CONSTRAINTS

Ref can also acts as constraint.

Even though vendors1 also holding vendor_adt, the orders table will store the object ids of vendors only because it is constrained to that table only.

The vendor_info column in the following syntaxes will store object ids of vendors only.

SQL> Create table orders (order_no number(2), vendor_info ref vendor_adt scope is

vendors);

SQL> Create table orders (order_no number(2), vendor_info ref vendor_adt constraint fk

references vendors);

AND HAVING

GROUP BY

Using group by, we can create groups of related information.

Columns used in select must be used with group by, otherwise it was not a group by expression.

Ex:

SQL> select deptno, sum(sal) from emp group by deptno;

DEPTNO SUM(SAL)

---------- ----------

10 8750

20 10875

30 9400

SQL> select deptno,job,sum(sal) from emp group by deptno,job;

DEPTNO JOB SUM(SAL)

---------- --------- ----------

10 CLERK 1300

10 MANAGER 2450

10 PRESIDENT 5000

20 ANALYST 6000

20 CLERK 1900

20 MANAGER 2975

30 CLERK 950

30 MANAGER 2850

30 SALESMAN 5600

HAVING

This will work as where clause which can be used only with group by because of absence of where clause in group by.

Ex:

SQL> select deptno,job,sum(sal) tsal from emp group by deptno,job having sum(sal) > 3000;

DEPTNO JOB TSAL

---------- --------- ----------

10 PRESIDENT 5000

20 ANALYST 6000

30 SALESMAN 5600

SQL> select deptno,job,sum(sal) tsal from emp group by deptno,job having sum(sal) > 3000

order by job;

DEPTNO JOB TSAL

---------- --------- ----------

20 ANALYST 6000

10 PRESIDENT 5000

30 SALESMAN 5600

ORDER OF EXECUTION

Group the rows together based on group by clause.

Calculate the group functions for each group.

Choose and eliminate the groups based on the having clause.

Order the groups based on the specified column.

ROLLUP GROUPING CUBE

These are the enhancements to the group by feature.

USING ROLLUP

This will give the salaries in each department in each job category along wih the total salary

fot individual departments and the total salary of all the departments.

SQL> Select deptno,job,sum(sal) from emp group by rollup(deptno,job);

DEPTNO JOB SUM(SAL)

---------- --------- ----------

10 CLERK 1300

10 MANAGER 2450

10 PRESIDENT 5000

10 8750

20 ANALYST 6000

20 CLERK 1900

20 MANAGER 2975

20 10875

30 CLERK 950

30 MANAGER 2850

30 SALESMAN 5600

30 9400

29025

USING GROUPING

In the above query it will give the total salary of the individual departments but with a

blank in the job column and gives the total salary of all the departments with blanks in

deptno and job columns.

To replace these blanks with your desired string grouping will be used

SQL> select decode(grouping(deptno),1,'All Depts',deptno),decode(grouping(job),1,'All

jobs',job),sum(sal) from emp group by rollup(deptno,job);

DECODE(GROUPING(DEPTNO),1,'ALLDEPTS',DEP DECODE(GR SUM(SAL)

----------------------------------- ---------------------------------- --------------

10 CLERK 1300

10 MANAGER 2450

10 PRESIDENT 5000

10 All jobs 8750

20 ANALYST 6000

20 CLERK 1900

20 MANAGER 2975

20 All jobs 10875

30 CLERK 950

30 MANAGER 2850

30 SALESMAN 5600

30 All jobs 9400

All Depts All jobs 29025

Grouping will return 1 if the column which is specified in the grouping function has been

used in rollup.

Grouping will be used in association with decode.

USING CUBE

This will give the salaries in each department in each job category, the total salary for individual departments, the total salary of all the departments and the salaries in each job category.

SQL> select decode(grouping(deptno),1,’All Depts’,deptno),decode(grouping(job),1,’All

Jobs’,job),sum(sal) from emp group by cube(deptno,job);

DECODE(GROUPING(DEPTNO),1,'ALLDEPTS',DEP DECODE(GR SUM(SAL)

----------------------------------- ------------------------------------ ------------

10 CLERK 1300

10 MANAGER 2450

10 PRESIDENT 5000

10 All Jobs 8750

20 ANALYST 6000

20 CLERK 1900

20 MANAGER 2975

20 All Jobs 10875

30 CLERK 950

30 MANAGER 2850

30 SALESMAN 5600

30 All Jobs 9400

All Depts ANALYST 6000

All Depts CLERK 4150

All Depts MANAGER 8275

All Depts PRESIDENT 5000

All Depts SALESMAN 5600

All Depts All Jobs 29025

PARTITIONS

A single logical table can be split into a number of physically separate pieces based on ranges of key values. Each of the parts of the table is called a partition.

A non-partitioned table can not be partitioned later.

TYPES

Range partitions

List partitions

Hash partitions

Sub partitions

ADVANTAGES

Reducing downtime for scheduled maintenance, which allows maintenance operations to be carried out on selected partitions while other partitions are available to users.

Reducing downtime due to data failure, failure of a particular partition will no way affect other partitions.

Partition independence allows for concurrent use of the various partitions for various purposes.

ADVANTAGES OF PARTITIONS BY STORING THEM IN DIFFERENT TABLESPACES

Reduces the possibility of data corruption in multiple partitions.

Back up and recovery of each partition can be done independently.

DISADVANTAGES

Partitioned tables cannot contain any columns with long or long raw datatypes, LOB types or object types.

RANGE PARTITIONS

a) Creating range partitioned table

SQL> Create table student(no number(2),name varchar(2)) partition by range(no) (partition

p1 values less than(10), partition p2 values less than(20), partition p3 values less

than(30),partition p4 values less than(maxvalue));

** if you are using maxvalue for the last partition, you can not add a partition.

b) Inserting records into range partitioned table

SQL> Insert into student values(1,’a’); -- this will go to p1

SQL> Insert into student values(11,’b’); -- this will go to p2

SQL> Insert into student values(21,’c’); -- this will go to p3

SQL> Insert into student values(31,’d’); -- this will go to p4

c) Retrieving records from range partitioned table

SQL> Select *from student;

SQL> Select *from student partition(p1);

d) Possible operations with range partitions

v Add

v Drop

v Truncate

v Rename

v Split

v Move

v Exchange

e) Adding a partition

SQL> Alter table student add partition p5 values less than(40);

f) Dropping a partition

SQL> Alter table student drop partition p4;

g) Renaming a partition

SQL> Alter table student rename partition p3 to p6;

h) Truncate a partition

SQL> Alter table student truncate partition p6;

i) Splitting a partition

SQL> Alter table student split partition p2 at(15) into (partition p21,partition p22);

j) Exchanging a partition

SQL> Alter table student exchange partition p1 with table student2;

k) Moving a partition

SQL> Alter table student move partition p21 tablespace saketh_ts;

LIST PARTITIONS

a) Creating list partitioned table

SQL> Create table student(no number(2),name varchar(2)) partition by list(no) (partition p1

values(1,2,3,4,5), partition p2 values(6,7,8,9,10),partition p3 values(11,12,13,14,15),

partition p4 values(16,17,18,19,20));

b) Inserting records into list partitioned table

SQL> Insert into student values(1,’a’); -- this will go to p1

SQL> Insert into student values(6,’b’); -- this will go to p2

SQL> Insert into student values(11,’c’); -- this will go to p3

SQL> Insert into student values(16,’d’); -- this will go to p4

c) Retrieving records from list partitioned table

SQL> Select *from student;

SQL> Select *from student partition(p1);

d) Possible operations with list partitions

v Add

v Drop

v Truncate

v Rename

v Move

v Exchange

e) Adding a partition

SQL> Alter table student add partition p5 values(21,22,23,24,25);

f) Dropping a partition

SQL> Alter table student drop partition p4;

g) Renaming a partition

SQL> Alter table student rename partition p3 to p6;

h) Truncate a partition

SQL> Alter table student truncate partition p6;

i) Exchanging a partition

SQL> Alter table student exchange partition p1 with table student2;

j) Moving a partition

SQL> Alter table student move partition p2 tablespace saketh_ts;

HASH PARTITIONS

a) Creating hash partitioned table

SQL> Create table student(no number(2),name varchar(2)) partition by hash(no) partitions

Here oracle automatically gives partition names like

SYS_P1

SYS_P2

SYS_P3

SYS_P4

SYS_P5

b) Inserting records into hash partitioned table

it will insert the records based on hash function calculated by taking the partition key

SQL> Insert into student values(1,’a’);

SQL> Insert into student values(6,’b’);

SQL> Insert into student values(11,’c’);

SQL> Insert into student values(16,’d’);

c) Retrieving records from hash partitioned table

SQL> Select *from student;

SQL> Select *from student partition(sys_p1);

d) Possible operations with hash partitions

v Add

v Truncate

v Rename

v Move

v Exchange

e) Adding a partition

SQL> Alter table student add partition p6 ;

f) Renaming a partition

SQL> Alter table student rename partition p6 to p7;

g) Truncate a partition

SQL> Alter table student truncate partition p7;

h) Exchanging a partition

SQL> Alter table student exchange partition sys_p1 with table student2;

i) Moving a partition

SQL> Alter table student move partition sys_p2 tablespace saketh_ts;

SUB-PARTITIONS WITH RANGE AND HASH

Subpartitions clause is used by hash only. We can not create subpartitions with list and hash partitions.

a) Creating subpartitioned table

SQL> Create table student(no number(2),name varchar(2),marks number(3))

Partition by range(no) subpartition by hash(name) subpartitions 3

(Partition p1 values less than(10),partition p2 values less than(20));

This will create two partitions p1 and p2 with three subpartitions for each partition

P1 – SYS_SUBP1

SYS_SUBP2

SYS_SUBP3

P2 – SYS_SUBP4

SYS_SUBP5

SYS_SUBP6

** if you are using maxvalue for the last partition, you can not add a partition.

b) Inserting records into subpartitioned table

SQL> Insert into student values(1,’a’); -- this will go to p1

SQL> Insert into student values(11,’b’); -- this will go to p2

c) Retrieving records from subpartitioned table

SQL> Select *from student;

SQL> Select *from student partition(p1);

SQL> Select *from student subpartition(sys_subp1);

d) Possible operations with subpartitions

v Add

v Drop

v Truncate

v Rename

v Split

e) Adding a partition

SQL> Alter table student add partition p3 values less than(30);

f) Dropping a partition

SQL> Alter table student drop partition p3;

g) Renaming a partition

SQL> Alter table student rename partition p2 to p3;

h) Truncate a partition

SQL> Alter table student truncate partition p1;

i) Splitting a partition

SQL> Alter table student split partition p3 at(15) into (partition p31,partition p32);

DATA MODEL

ALL_IND_PARTITIONS

ALL_IND_SUBPARTITIONS

ALL_TAB_PARTITIONS

ALL_TAB_SUBPARTITIONS

DBA_IND_PARTITIONS

DBA_IND_SUBPARTITIONS

DBA_TAB_PARTITIONS

DBA_TAB_SUBPARTITIONS

USER_IND_PARTITIONS

USER_IND_SUBPARTITIONS

USER_TAB_PARTITIONS

USER_TAB_SUBPARTITIONS

SET OPERATORS

TYPES

Union

Union all

Intersect

Minus

UNION

This will combine the records of multiple tables having the same structure.

Ex:

SQL> select * from student1 union select * from student2;

UNION ALL

This will combine the records of multiple tables having the same structure but including duplicates.

Ex:

SQL> select * from student1 union all select * from student2;

INTERSECT

This will give the common records of multiple tables having the same structure.

Ex:

SQL> select * from student1 intersect select * from student2;

MINUS

This will give the records of a table whose records are not in other tables having the same structure.

Ex:

SQL> select * from student1 minus select * from student2;

CASE AND DEFAULT

CASE

Case is similar to decode but easier to understand while going through coding

Ex:

SQL> Select sal,

Case sal

When 500 then ‘low’

When 5000 then ‘high’

Else ‘medium’

End case

From emp;

SAL CASE

----- --------

500 low

2500 medium

2000 medium

3500 medium

3000 medium

5000 high

4000 medium

5000 high

1800 medium

1200 medium

2000 medium

2700 medium

2200 medium

3200 medium

DEFAULT

Default can be considered as a substitute behavior of not null constraint when applied to new rows being entered into the table.

When you define a column with the default keyword followed by a value, you are actually telling the database that, on insert if a row was not assigned a value for this column, use the default value that you have specified.

Default is applied only during insertion of new rows.

Ex:

SQL> create table student(no number(2) default 11,name varchar(2));

SQL> insert into student values(1,'a');

SQL> insert into student(name) values('b');

SQL> select * from student;

NO NAME

------ ---------

1 a

11 b

SQL> insert into student values(null, ‘c’);

SQL> select * from student;

NO NAME

------ ---------

1 a

11 b

-- Default can not override nulls.

JOINS

The purpose of a join is to combine the data across tables.

A join is actually performed by the where clause which combines the specified rows of tables.

If a join involves in more than two tables then oracle joins first two tables based on the joins condition and then compares the result with the next table and so on.

TYPES

Equi join

Non-equi join

Self join

Natural join

Cross join

Outer join

Left outer

Right outer

Full outer

Inner join

Using clause

On clause

Assume that we have the following tables.

SQL> select * from dept;

DEPTNO DNAME LOC

------ ---------- ----------

10 mkt hyd

20 fin bang

30 hr bombay

SQL> select * from emp;

EMPNO ENAME JOB MGR DEPTNO

---------- ---------- ---------- ---------- ----------

111 saketh analyst 444 10

222 sudha clerk 333 20

333 jagan manager 111 10

444 madhu engineer 222 40

EQUI JOIN

A join which contains an ‘=’ operator in the joins condition.

Ex:

SQL> select empno,ename,job,dname,loc from emp e,dept d where e.deptno=d.deptno;

EMPNO ENAME JOB DNAME LOC

---------- ---------- ---------- ---------- ----------

111 saketh analyst mkt hyd

333 jagan manager mkt hyd

222 sudha clerk fin bang

USING CLAUSE

SQL> select empno,ename,job ,dname,loc from emp e join dept d using(deptno);

EMPNO ENAME JOB DNAME LOC

---------- ---------- ---------- ---------- ----------

111 saketh analyst mkt hyd

333 jagan manager mkt hyd

222 sudha clerk fin bang

ON CLAUSE

SQL> select empno,ename,job,dname,loc from emp e join dept d on(e.deptno=d.deptno);

EMPNO ENAME JOB DNAME LOC

---------- ---------- ---------- ---------- ----------

111 saketh analyst mkt hyd

333 jagan manager mkt hyd

222 sudha clerk fin bang

NON-EQUI JOIN

A join which contains an operator other than ‘=’ in the joins condition.

Ex:

SQL> select empno,ename,job,dname,loc from emp e,dept d where e.deptno > d.deptno;

EMPNO ENAME JOB DNAME LOC

---------- ---------- ---------- ---------- ----------

222 sudha clerk mkt hyd

444 madhu engineer mkt hyd

444 madhu engineer fin bang

444 madhu engineer hr bombay

SELF JOIN

Joining the table itself is called self join.

Ex:

SQL> select e1.empno,e2.ename,e1.job,e2.deptno from emp e1,emp e2 where

e1.empno=e2.mgr;

EMPNO ENAME JOB DEPTNO

---------- ---------- ---------- ----------

111 jagan analyst 10

222 madhu clerk 40

333 sudha manager 20

444 saketh engineer 10

NATURAL JOIN

Natural join compares all the common columns.

Ex:

SQL> select empno,ename,job,dname,loc from emp natural join dept;

EMPNO ENAME JOB DNAME LOC

---------- ---------- ---------- ---------- ----------

111 saketh analyst mkt hyd

333 jagan manager mkt hyd

222 sudha clerk fin bang

CROSS JOIN

This will gives the cross product.

Ex:

SQL> select empno,ename,job,dname,loc from emp cross join dept;

EMPNO ENAME JOB DNAME LOC

---------- ---------- ---------- ---------- ----------

111 saketh analyst mkt hyd

222 sudha clerk mkt hyd

333 jagan manager mkt hyd

444 madhu engineer mkt hyd

111 saketh analyst fin bang

222 sudha clerk fin bang

333 jagan manager fin bang

444 madhu engineer fin bang

111 saketh analyst hr bombay

222 sudha clerk hr bombay

333 jagan manager hr bombay

444 madhu engineer hr bombay

OUTER JOIN

Outer join gives the non-matching records along with matching records.

LEFT OUTER JOIN

This will display the all matching records and the records which are in left hand side table those that are not in right hand side table.

Ex:

SQL> select empno,ename,job,dname,loc from emp e left outer join dept d

on(e.deptno=d.deptno);

SQL> select empno,ename,job,dname,loc from emp e,dept d where e.deptno=d.deptno(+);

EMPNO ENAME JOB DNAME LOC

---------- ---------- ---------- ---------- ----------

111 saketh analyst mkt hyd

333 jagan manager mkt hyd

222 sudha clerk fin bang

444 madhu engineer

RIGHT OUTER JOIN

This will display the all matching records and the records which are in right hand side table those that are not in left hand side table.

Ex:

SQL> select empno,ename,job,dname,loc from emp e right outer join dept d

on(e.deptno=d.deptno);

SQL> select empno,ename,job,dname,loc from emp e,dept d where e.deptno(+) = d.deptno;

EMPNO ENAME JOB DNAME LOC

---------- ---------- ---------- ---------- ----------

111 saketh analyst mkt hyd

333 jagan manager mkt hyd

222 sudha clerk fin bang

hr bombay

FULL OUTER JOIN

This will display the all matching records and the non-matching records from both tables.

Ex:

SQL> select empno,ename,job,dname,loc from emp e full outer join dept d

on(e.deptno=d.deptno);

EMPNO ENAME JOB DNAME LOC

---------- ---------- ---------- ---------- ----------

333 jagan manager mkt hyd

111 saketh analyst mkt hyd

222 sudha clerk fin bang

444 madhu engineer

hr bombay

INNER JOIN

This will display all the records that have matched.

Ex:

SQL> select empno,ename,job,dname,loc from emp inner join dept using(deptno);

EMPNO ENAME JOB DNAME LOC

---------- ---------- ---------- ---------- ----------

111 saketh analyst mkt hyd

333 jagan manager mkt hyd

222 sudha clerk fin bang

VIEWS

A view is a database object that is a logical representation of a table. It is delivered from a table but has no storage of its own and often may be used in the same manner as a table.

A view takes the output of the query and treats it as a table, therefore a view can be thought of as a stored query or a virtual table.

TYPES

Simple view

Complex view

Simple view can be created from one table where as complex view can be created from multiple tables.

WHY VIEWS?

Provides additional level of security by restricting access to a predetermined set of rows and/or columns of a table.

Hide the data complexity.

Simplify commands for the user.

VIEWS WITHOUT DML

Read only view

View with group by

View with aggregate functions

View with rownum

Partition view

View with distinct

Ex:

SQL> Create view dept_v as select *from dept with read only;

SQL> Create view dept_v as select deptno, sum(sal) t_sal from emp group by deptno;

SQL> Create view stud as select rownum no, name, marks from student;

SQL> Create view student as select *from student1 union select *from student2;

SQL> Create view stud as select distinct no,name from student;

VIEWS WITH DML

View with not null column -- insert with out not null column not possible

-- update not null column to null is not possible

-- delete possible

View with out not null column which was in base table -- insert not possible

-- update, delete possible

View with expression -- insert , update not possible

-- delete possible

View with functions (except aggregate) -- insert, update not possible

-- delete possible

View was created but the underlying table was dropped then we will get the message like “ view has errors ”.

View was created but the base table has been altered but still the view was with the initial definition, we have to replace the view to affect the changes.

Complex view (view with more than one table) -- insert not possible

-- update, delete possible (not always)

CREATING VIEW WITHOUT HAVING THE BASE TABLE

SQL> Create force view stud as select *From student;

-- Once the base table was created then the view is validated.

VIEW WITH CHECK OPTION CONSTRAINT

SQL> Create view stud as select *from student where marks = 500 with check option constraint

Ck;

- Insert possible with marks value as 500

- Update possible excluding marks column

- Delete possible

DROPPING VIEWS

SQL> drop view dept_v;

SUBQUERIES AND EXISTS

SUBQUERIES

Nesting of queries, one within the other is termed as a subquery.

A statement containing a subquery is called a parent query.

Subqueries are used to retrieve data from tables that depend on the values in the table itself.

TYPES

Single row subqueries

Multi row subqueries

Multiple subqueries

Correlated subqueries

SINGLE ROW SUBQUERIES

In single row subquery, it will return one value.

Ex:

SQL> select * from emp where sal > (select sal from emp where empno = 7566);

EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO

---------- ---------- --------- ---------- ------------ ------- ---------- ----------

7788 SCOTT ANALYST 7566 19-APR-87 3000 20

7839 KING PRESIDENT 17-NOV-81 5000 10

7902 FORD ANALYST 7566 03-DEC-81 3000 20

MULTI ROW SUBQUERIES

In multi row subquery, it will return more than one value. In such cases we should include operators like any, all, in or not in between the comparision operator and the subquery.

Ex:

SQL> select * from emp where sal > any (select sal from emp where sal between 2500 and

4000);

EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO

---------- ---------- --------- ---------- ----------- -------- ---------- ----------

7566 JONES MANAGER 7839 02-APR-81 2975 20

7788 SCOTT ANALYST 7566 19-APR-87 3000 20

7839 KING PRESIDENT 17-NOV-81 5000 10

7902 FORD ANALYST 7566 03-DEC-81 3000 20

SQL> select * from emp where sal > all (select sal from emp where sal between 2500 and

4000);

EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO

---------- ---------- --------- ---------- ------------- ------ ---------- ----------

7839 KING PRESIDENT 17-NOV-81 5000 10

MULTIPLE SUBQUERIES

There is no limit on the number of subqueries included in a where clause. It allows nesting of a query within a subquery.

Ex:

SQL> select * from emp where sal = (select max(sal) from emp where sal < (select

max(sal) from emp));

EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO

---------- ---------- --------- ---------- ------------ ------- ---------- ----------

7788 SCOTT ANALYST 7566 19-APR-87 3000 20

7902 FORD ANALYST 7566 03-DEC-81 3000 20

CORRELATED SUBQUERIES

A subquery is evaluated once for the entire parent statement where as a correlated subquery is evaluated once for every row processed by the parent statement.

Ex:

SQL> select distinct deptno from emp e where 5 <= (select count(ename) from emp where

e.deptno = deptno);

DEPTNO

----------

EXISTS

Exists function is a test for existence. This is a logical test for the return of rows from a query.

Ex:

Suppose we want to display the department numbers which has more than 4 employees.

SQL> select deptno,count(*) from emp group by deptno having count(*) > 4;

DEPTNO COUNT(*)

--------- ----------

20 5

30 6

From the above query can you want to display the names of employees?

SQL> select deptno,ename, count(*) from emp group by deptno,ename having count(*) > 4;

no rows selected

The above query returns nothing because combination of deptno and ename never return

more than one count.

The solution is to use exists which follows.

SQL> select deptno,ename from emp e1 where exists (select * from emp e2

where e1.deptno=e2.deptno group by e2.deptno having count(e2.ename) > 4) order by

deptno,ename;

DEPTNO ENAME

---------- ----------

20 ADAMS

20 FORD

20 JONES

20 SCOTT

20 SMITH

30 ALLEN

30 BLAKE

30 JAMES

30 MARTIN

30 TURNER

30 WARD

NOT EXISTS

SQL> select deptno,ename from emp e1 where not exists (select * from emp e2

where e1.deptno=e2.deptno group by e2.deptno having count(e2.ename) > 4) order by

deptno,ename;

DEPTNO ENAME

--------- ----------

10 CLARK

10 KING

10 MILLER

SYNONYM AND SEQUENCE

SYNONYM

A synonym is a database object, which is used as an alias for a table, view or sequence.

TYPES

Private

Public

Private synonym is available to the particular user who creates.

Public synonym is created by DBA which is available to all the users.

ADVANTAGES

Hide the name and owner of the object.

Provides location transparency for remote objects of a distributed database.

CREATE AND DROP

SQL> create synonym s1 for emp;

SQL> create public synonym s2 for emp;

SQL> drop synonym s1;

SEQUENCE

A sequence is a database object, which can generate unique, sequential integer values.

It can be used to automatically generate primary key or unique key values.

A sequence can be either in an ascending or descending order.

Syntax:

Create sequence <seq_name> [increment bty n] [start with n] [maxvalue n] [minvalue n]

[cycle/nocycle] [cache/nocache];

By defalult the sequence starts with 1, increments by 1 with minvalue of 1 and with nocycle, nocache.

Cache option pre-alloocates a set of sequence numbers and retains them in memory for faster access.

Ex:

SQL> create sequence s;

SQL> create sequence s increment by 10 start with 100 minvalue 5 maxvalue 200 cycle

cache 20;

USING SEQUENCE

SQL> create table student(no number(2),name varchar(10));

SQL> insert into student values(s.nextval, ‘saketh’);

Initially currval is not defined and nextval is starting value.

After that nextval and currval are always equal.

CREATING ALPHA-NUMERIC SEQUENCE

SQL> create sequence s start with 111234;

SQL> Insert into student values (s.nextval || translate

(s.nextval,’1234567890’,’abcdefghij’));

ALTERING SEQUENCE

We can alter the sequence to perform the following.

Set or eliminate minvalue or maxvalue.

Change the increment value.

Change the number of cached sequence numbers.

Ex:

SQL> alter sequence s minvalue 5;

SQL> alter sequence s increment by 2;

SQL> alter sequence s cache 10;

DROPPING SEQUENCE

SQL> drop sequence s;

INDEXES

Index is typically a listing of keywords accompanied by the location of information on a subject. We can create indexes explicitly to speed up SQL statement execution on a table. The index points directly to the location of the rows containing the value.

WHY INDEXES?

Indexes are most useful on larger tables, on columns that are likely to appear in where clauses as simple equality.

TYPES

Unique index

Non-unique index

Btree index

Bitmap index

Composite index

Reverse key index

Function-based index

Descending index

Domain index

Object index

Cluster index

Text index

Index organized table

Partition index

v Local index

ü Local prefixed

ü Local non-prefixed

v Global index

ü Global prefixed

ü Global non-prefixed

UNIQUE INDEX

Unique indexes guarantee that no two rows of a table have duplicate values in the columns that define the index. Unique index is automatically created when primary key or unique constraint is created.

Ex:

SQL> create unique index stud_ind on student(sno);

NON-UNIQUE INDEX

Non-Unique indexes do not impose the above restriction on the column values.

Ex:

SQL> create index stud_ind on student(sno);

BTREE INDEX or ASCENDING INDEX

The default type of index used in an oracle database is the btree index. A btree index is designed to provide both rapid access to individual rows and quick access to groups of rows within a range. The btree index does this by performing a succession of value comparisons. Each comparison eliminates many of the rows.

Ex:

SQL> create index stud_ind on student(sno);

BITMAP INDEX

This can be used for low cardinality columns: that is columns in which the number of distinct values is snall when compared to the number of the rows in the table.

Ex:

SQL> create bitmap index stud_ind on student(sex);

COMPOSITE INDEX

A composite index also called a concatenated index is an index created on multiple columns of a table. Columns in a composite index can appear in any order and need not be adjacent columns of the table.

Ex:

SQL> create bitmap index stud_ind on student(sno, sname);

REVERSE KEY INDEX

A reverse key index when compared to standard index, reverses each byte of the column being indexed while keeping the column order. When the column is indexed in reverse mode then the column values will be stored in an index in different blocks as the starting value differs. Such an arrangement can help avoid performance degradations in indexes where modifications to the index are concentrated on a small set of blocks.

Ex:

SQL> create index stud_ind on student(sno, reverse);

We can rebuild a reverse key index into normal index using the noreverse keyword.

Ex:

SQL> alter index stud_ind rebuild noreverse;

FUNCTION BASED INDEX

This will use result of the function as key instead of using column as the value for the key.

Ex:

SQL> create index stud_ind on student(upper(sname));

DESCENDING INDEX

The order used by B-tree indexes has been ascending order. You can categorize data in B-tree index in descending order as well. This feature can be useful in applications where sorting operations are required.

Ex:

SQL> create index stud_ind on student(sno desc);

TEXT INDEX

Querying text is different from querying data because words have shades of meaning, relationships to other words, and opposites. You may want to search for words that are near each other, or words that are related to thers. These queries would be extremely difficult if all you had available was the standard relational operators. By extending SQL to include text indexes, oracle text permits you to ask very complex questions about the text.

To use oracle text, you need to create a text index on the column in which the text is stored. Text index is a collection of tables and indexes that store information about the text stored in the column.

TYPES

There are several different types of indexes available in oracle 9i. The first, CONTEXT is supported in oracle 8i as well as oracle 9i. As of oracle 9i, you can use the CTXCAT text index fo further enhance your text index management and query capabilities.

CONTEXT

CTXCAT

CTXRULE

The CTXCAT index type supports the transactional synchronization of data between the base table and its text index. With CONTEXT indexes, you need to manually tell oracle to update the values in the text index after data changes in base table. CTXCAT index types do not generate score values during the text queries.

HOW TO CREATE TEXT INDEX?

You can create a text index via a special version of the create index comman. For context index, specify the ctxsys.context index type and for ctxcat index, specify the ctxsys.ctxcat index type.

Ex:

Suppose you have a table called BOOKS with the following columns

Title, Author, Info.

SQL> create index book_index on books(info) indextype is ctxsys.context;

SQL> create index book_index on books(info) indextype is ctxsys.ctxcat;

TEXT QUERIES

Once a text index is created on the info column of BOOKS table, text-searching capabilities increase dynamically.

CONTAINS & CATSEARCH

CONTAINS function takes two parameters – the column name and the search string.

Syntax:

Contains(indexed_column, search_str);

If you create a CTXCAT index, use the CATSEARCH function in place of CONTAINS. CATSEARCH takes three parameters – the column name, the search string and the index set.

Syntax:

Contains(indexed_column, search_str, index_set);

HOW A TEXT QEURY WORKS?

When a function such as CONTAINS or CATSEARCH is used in query, the text portion of the query is processed by oracle text. The remainder of the query is processed just like a regular query within the database. The result of the text query processing and the regular query processing are merged to return a single set of records to the user.

SEARCHING FOR AN EXACT MATCH OF A WORD

The following queries will search for a word called ‘prperty’ whose score is greater than zero.

SQL> select * from books where contains(info, ‘property’) > 0;

SQL> select * from books where catsearch(info, ‘property’, null) > 0;

Suppose if you want to know the score of the ‘property’ in each book, if score values for individual searches range from 0 to 10 for each occurrence of the string within the text then use the score function.

SQL> select title, score(10) from books where contains(info, ‘property’, 10) > 0;

SEARCHING FOR AN EXACT MATCH OF MULTIPLE WORDS

The following queries will search for two words.

SQL> select * from books where contains(info, ‘property AND harvests’) > 0;

SQL> select * from books where catsearch(info, ‘property AND harvests’, null) > 0;

Instead of using AND you could hae used an ampersand(&). Before using this method, set define off so the & character will not be seen as part of a variable name.

SQL> set define off

SQL> select * from books where contains(info, ‘property & harvests’) > 0;

SQL> select * from books where catsearch(info, ‘property harvests’, null) > 0;

The following queries will search for more than two words.

SQL> select * from books where contains(info, ‘property AND harvests AND workers’) > 0;

SQL> select * from books where catsearch(info, ‘property harvests workers’, null) > 0;

The following queries will search for either of the two words.

SQL> select * from books where contains(info, ‘property OR harvests’) > 0;

Instead of OR you can use a vertical line (|).

SQL> select * from books where contains(info, ‘property | harvests’) > 0;

SQL> select * from books where catsearch(info, ‘property | harvests’, null) > 0;

In the following queries the ACCUM(accumulate) operator adds together the scores of the individual searches and compares the accumulated score to the threshold value.

SQL> select * from books where contains(info, ‘property ACCUM harvests’) > 0;

SQL> select * from books where catsearch(info, ‘property ACCUM harvests’, null) > 0;

Instead of OR you can use a comma(,).

SQL> select * from books where contains(info, ‘property , harvests’) > 0;

SQL> select * from books where catsearch(info, ‘property , harvests’, null) > 0;

In the following queries the MINUS operator subtracts the score of the second term’s search from the score of the first term’s search.

SQL> select * from books where contains(info, ‘property MINUS harvests’) > 0;

SQL> select * from books where catsearch(info, ‘property NOT harvests’, null) > 0;

Instead of MINUS you can use – and instead of NOT you can use ~.

SQL> select * from books where contains(info, ‘property - harvests’) > 0;

SQL> select * from books where catsearch(info, ‘property ~ harvests’, null) > 0;

SEARCHING FOR AN EXACT MATCH OF A PHRASE

The following queries will search for the phrase. If the search phrase includes a reserved word within oracle text, the you must use curly braces ({}) to enclose text.

SQL> select * from books where contains(info, ‘transactions {and} finances’) > 0;

SQL> select * from books where catsearch(info, ‘transactions {and} finances’, null) > 0;

You can enclose the entire phrase within curly braces, in which case any reserved words within the phrase will be treated as part of the search criteria.

SQL> select * from books where contains(info, ‘{transactions and finances}’) > 0;

SQL> select * from books where catsearch(info, ‘{transactions and finances}’, null) > 0;

SEARCHING FOR WORDS THAT ARE NEAR EACH OTHER

The following queries will search for the words that are in between the search terms.

SQL> select * from books where contains(info, ‘workers NEAR harvests’) > 0;

Instead of NEAR you can use ;.

SQL> select * from books where contains(info, ‘workers ; harvests’) > 0;

In CONTEXT index queries, you can specify the maximum number of words between the search terms.

SQL> select * from books where contains(info, ‘NEAR((workers, harvests),10)’ > 0;

USING WILDCARDS DURING SEARCHES

You can use wildcards to expand the list of valid search terms used during your query. Just as in regular text-string wildcard processing, two wildcards are available.

% - percent sign; multiple-character wildcard

_ - underscore; single-character wildcard

SQL> select * from books where contains(info, ‘worker%’) > 0;

SQL> select * from books where contains(info, ‘work___’) > 0;

SEARCHING FOR WORDS THAT SHARE THE SAME STEM

Rather than using wildcards, you can use stem-expansion capabilities to expand the list of text strings. Given the ‘stem’ of a word, oracle will expand the list of words to search for to include all words having the same stem. Sample expansions are show here.

Play - plays playing played playful

SQL> select * from books where contains(info, ‘$manage’) > 0;

SEARCHING FOR FUZZY MATCHES

A fuzzy match expands the specified search term to include words that are spelled similarly but that do not necessarily have the same word stem. Fuzzy matches are most helpful when the text contains misspellings. The misspellings can be either in the searched text or in the search string specified by the user during the query.

The following queries will not return anything because its search does not contain the word ‘hardest’.

SQL> select * from books where contains(info, ‘hardest’) > 0;

It does, however, contains the word ‘harvest’. A fuzzy match will return the books containing the word ‘harvest’ even though ‘harvest’ has a different word stem thant the word used as the search term.

To use a fuzzy match, precede the search term with a question mark, with no space between the question mark and the beginning of the search term.

SQL> select * from books where contains(info, ‘?hardest’) > 0;

SEARCHING FOR WORDS THAT SOUND LIKE OTHER WORDS

SOUNDEX, expands search terms based on how the word sounds. The SOUNDEX expansion method uses the same text-matching logic available via the SOUNDEX function in SQL.

To use the SOUNDEX option, you must precede the search term with an exclamation mark(!).

SQL> select * from books where contains(info, ‘!grate’) > 0;

INDEX SYNCHRONIZATION

When using CONTEXT indexes, you need to manage the text index contents; the text indexes are not updated when the base table is updated. When the table was updated, its text index is out of sync with the base table. To sync of the index, execute the SYNC_INDEX procedure of the CTX_DDL package.

SQL> exec CTX_DDL.SYNC_INDEX(‘book_index’);

INDEX SETS

Historically, problems with queries of text indexes have occurred when other criteria are used alongside text searches as part of the where clause. To improve the mixed query capability, oracle features index sets. The indexes within the index set may be structured relational columns or on text columns.

To create an index set, use the CTX_DDL package to create the index set and add indexes to it. When you create a text index, you can then specify the index set it belongs to.

SQL> exec CTX_DDL.CREATE_INDEX_SET(‘books_index_set’);

The add non-text indexes.

SQL> exec CTX_DDL.ADD_INDEX(‘books_index_set’, ‘title_index’);

Now create a CTXCAT text index. Specify ctxsys.ctxcat as the index type, and list the index set in the parameters clause.

SQL> create index book_index on books(info) indextype is ctxsys.ctxcat parameters(‘index set books_index_set’);

INDEX-ORGANIZED TABLE

An index-organized table keeps its data sorted according to the primary key column values for the table. Index-organized tables store their data as if the entire table was stored in an index.

An index-organized table allows you to store the entire table’s data in an index.

Ex:

SQL> create table student (sno number(2),sname varchar(10),smarks number(3) constraint

pk primary key(sno) organization index;

PARTITION INDEX

Similar to partitioning tables, oracle allows you to partition indexes too. Like table partitions, index partitions could be in different tablespaces.

LOCAL INDEXES

Local keyword tells oracle to create a separte index for each partition.

In the local prefixed index the partition key is specified on the left prefix. When the underlying table is partitioned baes on, say two columns then the index can be prefixed on the first column specified.

Local prefixed indexes can be unique or non unique.

Local indexes may be easier to manage than global indexes.

Ex:

SQL> create index stud_index on student(sno) local;

GLOBAL INDEXES

A global index may contain values from multiple partitions.

An index is global prefixed if it is partitioned on the left prefix of the index columns.

The global clause allows you to create a non-partitioned index.

Global indexes may perform uniqueness checks faster than local (partitioned) indexes.

You cannot create global indexes for hash partitions or subpartitions.

Ex:

SQL> create index stud_index on student(sno) global;

Similar to table partitions, it is possible to move them from one device to another. But unlike table partitions, movement of index partitions requires individual reconstruction of the index or each partition (only in the case of global index).

Ex:

SQL> alter index stud_ind rebuild partition p2

Index partitions cannot be dropped manually.

They are dropped implicitly when the data they refer to is dropped from the partitioned table.

MONITORING USE OF INDEXES

Once you turned on the monitoring the use of indexes, then we can check whether the table is hitting the index or not.

To monitor the use of index use the follwing syntax.

Syntax:

alter index index_name monitoring usage;

then check for the details in V$OBJECT_USAGE view.

If you want to stop monitoring use the following.

Syntax:

alter index index_name nomonitoring usage;

DATA MODEL

ALL_INDEXES

DBA_INDEXES

USER_INDEXES

ALL_IND-COLUMNS

DBA-IND_COLUMNS

USER_IND_COLUMNS

ALL_PART_INDEXES

DBA_PART_INDEXES

USER_PART_INDEXES

LOCKS

Locks are the mechanisms used to prevent destructive interaction between users accessing same resource simultaneously. Locks provides high degree of data concurrency.

TYPES

Row level locks

Table level locks

ROW LEVEL LOCKS

In the row level lock a row is locked exclusively so that other cannot modify the row until the transaction holding the lock is committed or rolled back. This can be done by using select..for update clause.

Ex:

SQL> select * from emp where sal > 3000 for update of comm.;

TABLE LEVEL LOCKS

A table level lock will protect table data thereby guaranteeing data integrity when data is being accessed concurrently by multiple users. A table lock can be held in several modes.

Share lock

Share update lock

Exclusive lock

SHARE LOCK

A share lock locks the table allowing other users to only query but not insert, update or delete rows in a table. Multiple users can place share locks on the same resource at the same time.

Ex:

SQL> lock table emp in share mode;

SHARE UPDATE LOCK

It locks rows that are to be updated in a table. It permits other users to concurrently query, insert , update or even lock other rows in the same table. It prevents the other users from updating the row that has been locked.

Ex:

SQL> lock table emp in share update mode;

EXCLUSIVE LOCK

Exclusive lock is the most restrictive of tables locks. When issued by any user, it allows the other user to only query. It is similar to share lock but only one user can place exclusive lock on a table at a time.

Ex:

SQL> lock table emp in share exclusive mode;

NOWAIT

If one user locked the table without nowait then another user trying to lock the same table then he has to wait until the user who has initially locked the table issues a commit or rollback statement. This delay could be avoided by appending a nowait clause in the lock table command.

Ex:

SQL> lock table emp in exclusive mode nowait.

DEADLOCK

A deadlock occurs when tow users have a lock each on separate object, and they want to acquire a lock on the each other’s object. When this happens, the first user has to wait for the second user to release the lock, but the second user will not release it until the lock on the first user’s object is freed. In such a case, oracle detects the deadlock automatically and solves the problem by aborting one of the two transactions

WALKUP TREES AND INLINE VIEW

WALKUP TREES

Using hierarchical queries, you can retrieve data based on a natural hierarchical relationship between rows in a table. However, where a hierarchical relationship exists between the rows of a table, a process called tree walking enables the hierarchy to be constructed.

Ex:

SQL> select ename || '==>' || prior ename, level from emp start with ename = 'KING'

connect by prior empno=mgr;

ENAME||'==>'||PRIORENAM LEVEL

------------------------------------ --------

KING==> 1

JONES==>KING 2

SCOTT==>JONES 3

ADAMS==>SCOTT 4

FORD==>JONES 3

SMITH==>FORD 4

BLAKE==>KING 2

ALLEN==>BLAKE 3

WARD==>BLAKE 3

MARTIN==>BLAKE 3

TURNER==>BLAKE 3

JAMES==>BLAKE 3

CLARK==>KING 2

MILLER==>CLARK 3

In the above

Start with clause specifies the root row of the table.

Level pseudo column gives the 1 for root , 2 for child and so on.

Connect by prior clause specifies the columns which has parent-child relationship.

INLINE VIEW OR TOP-N ANALYSIS

In the select statement instead of table name, replacing the select statement is known as inline view.

Ex:

SQL> Select ename, sal, rownum rank from (select *from emp order by sal);

ENAME SAL RANK

---------- ---------- ----------

SMITH 800 1

JAMES 950 2

ADAMS 1100 3

WARD 1250 4

MARTIN 1250 5

MILLER 1300 6

TURNER 1500 7

ALLEN 1600 8

CLARK 2450 9

BLAKE 2850 10

JONES 2975 11

SCOTT 3000 12

FORD 3000 13

KING 5000 14

SET COMMANDS

These commands does not require statement terminator and applicable to the sessions , those will be automatically cleared when session was closed.

LINESIZE

This will be used to set the linesize. Default linesize is 80.

Syntax: Set linesize <value>

Ex:

SQL> set linesize 100

PAGESIZE

This will be used to set the pagesize. Default pagesize is 14.

Syntax:

Set pagesize <value>

Ex:

SQL> set pagesize 30

DESCRIBE

This will be used to see the object’s structure.

Syntax:

Describe or desc <object_name>

Ex:

SQL> desc dept

Name Null? Type

----------------------------------------------------------------- ---------------------

DEPTNO NOT NULL NUMBER(2)

DNAME VARCHAR2(14)

LOC VARCHAR2(13)

PAUSE

When the displayed data contains hundreds or thousands of lines, when you select it then it will automatically scrolls and displays the last page data. To prevent this you can use this pause option. By using this it will display the data correspoinding to the pagesize with a break which will continue by hitting the return key. By default this will be off.

Syntax:

Set pause on | off

Ex:

SQL> set pause on

FEEDBACK

This will give the information regarding howmany rows you selected the object. By default the feedback message will be displayed, only when the object contains more than 5 rows.

Syntax:

Set feedback <value>

Ex:

SQL> set feedback 4

SQL> select * from dept;

DEPTNO DNAME LOC

---------- -------------- -------------

10 ACCOUNTING NEW YORK

20 RESEARCH DALLAS

30 SALES CHICAGO

40 OPERATIONS BOSTON

4 rows selected.

HEADING

If you want to display data without headings, then you can achieve with this. By default heading is on.

Syntax:

Set heading on | off

Ex:

SQL> set heading off

SQL> select * from dept;

10 ACCOUNTING NEW YORK

20 RESEARCH DALLAS

30 SALES CHICAGO

40 OPERATIONS BOSTON

SERVEROUTPUT

This will be used to display the output of the PL/SQL programs. By default this will be off.

Syntax:

Set serveroutput on | off

Ex:

SQL> set serveroutput on

TIME

This will be used to display the time. By default this will be off.

Syntax:

Set time on | off

Ex:

SQL> set time on

19:56:33 SQL>

TIMING

This will give the time taken to execute the current SQL statement. By default this will be off.

Syntax:

Set timing on | off

Ex:

SQL> set timing on

SQL> select * from dept;

DEPTNO DNAME LOC

---------- -------------- -------------

10 ACCOUNTING NEW YORK

20 RESEARCH DALLAS

30 SALES CHICAGO

40 OPERATIONS BOSTON

Elapsed: 00:00:00.06

SQLPROMPT

This will be used to change the SQL prompt.

Syntax:

Set sqlprompt <prompt>

Ex:

SQL> set sqlprompt 'ORACLE>'

ORACLE>

SQLCASE

This will be used to change the case of the SQL statements. By default the case is mixed.

Syntax:

Set sqlcase upper | mixed | lower

Ex:

SQL> set sqlcase upper

SQLTERMINATOR

This will be used to change the terminator of the SQL statements. By default the terminator is ;.

Syntax:

Set sqlterminator <termination_character>

Ex:

SQL> set sqlterminator :

SQL> select * from dept:

DEFINE

By default if the & character finds then it will treat as bind variable and ask for the input. Suppose your want to treat it as a normal character while inserting data, then you can prevent this by using the define option. By default this will be on

Syntax:

Set define on | off

Ex:

SQL>insert into dept values(50,'R&D','HYD');

Enter value for d:

old 1: insert into dept values(50,'R&D','HYD')

new 1: INSERT INTO DEPT VALUES(50,'R','HYD')

SQL> set define off

SQL>insert into dept values(50,'R&D','HYD'); -- here it won’t ask for value

ECHO

VERIFY

NEWPAGE

HEADSEP

PNO

SQL*PLUS COMMNANDS

These commands does not require statement terminator and applicable to the sessions , those will be automatically cleared when session was closed.

BREAK

This will be used to breakup the data depending on the grouping.

Syntax:

Break or bre [on <column_name> on report]

COMPUTE

This will be used to perform group functions on the data.

Syntax:

Compute or comp [group_function of column_name on breaking_column_name or

report]

TTITLE

This will give the top title for your report. You can on or off the ttitle.

Syntax:

Ttitle or ttit [left | center | right] title_name skip n other_characters

Ttitle or ttit [on or off]

BTITLE

This will give the bottom title for your report. You can on or off the btitle.

Syntax:

Btitle or btit [left | center | right] title_name skip n other_characters

Btitle or btit [on or off]

Ex:

SQL> bre on deptno skip 1 on report

SQL> comp sum of sal on deptno

SQL> comp sum of sal on report

SQL> ttitle center 'EMPLOYEE DETAILS' skip1 center '----------------'

SQL> btitle center '** THANKQ **'

SQL> select * from emp order by deptno;

Output:

EMPLOYEE DETAILS

-----------------------

EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO

---------- ---------- --------- ------- -------------- -------- ---------- ----------

7782 CLARK MANAGER 7839 09-JUN-81 2450 10

7839 KING PRESIDENT 17-NOV-81 5000

7934 MILLER CLERK 7782 23-JAN-82 1300

---------- **********

8750 sum

7369 SMITH CLERK 7902 17-DEC-80 800 20

7876 ADAMS CLERK 7788 23-MAY-87 1100

7902 FORD ANALYST 7566 03-DEC-81 3000

7788 SCOTT ANALYST 7566 19-APR-87 3000

7566 JONES MANAGER 7839 02-APR-81 2975

---------- **********

10875 sum

7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30

7698 BLAKE MANAGER 7839 01-MAY-81 2850

7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400

7900 JAMES CLERK 7698 03-DEC-81 950

7844 TURNER SALESMAN 7698 08-SEP-81 1500 0

7521 WARD SALESMAN 7698 22-FEB-81 1250 500

---------- **********

9400 sum

----------

sum 29025

** THANKQ **

CLEAR

This will clear the existing buffers or break or computations.

Syntax:

Clear or cle buffer | bre | comp;

Ex:

SQL> clear buffer

Buffer cleared

SQL> clear bre

Breaks cleared

SQL> clear comp

Computes cleared

CHANGE

This will be used to replace any strings in SQL statements.

Syntax:

Change or c/old_string/new_string

If the old_string repeats many times then new_string replaces the first string only.

Ex:

SQL> select * from det;

select * from det

ERROR at line 1:

ORA-00942: table or view does not exist

SQL> c/det/dept

1* select * from dept

SQL> /

DEPTNO DNAME LOC

---------- ---------------- -----------

10 ACCOUNTING NEW YORK

20 RESEARCH ALLAS

30 SALES CHICAGO

40 OPERATIONS BOSTON

COLUMN

This will be used to increase or decrease the width of the table columns.

Syntax:

Column or col <column_name> format <num_format|text_format>

Ex:

SQL> col deptno format 999

SQL> col dname format a10

SAVE

This will be used to save your current SQL statement as SQL Script file.

Syntax:

Save or sav <file_name>.[extension] replace or rep

If you want to save the filename with existing filename the you have to use replace option.

By default it will take sql as the extension.

Ex:

SQL> save ss

Created file ss.sql

SQL> save ss replace

Wrote file ss.sql

SQL> @ss.sql -- this will execute sql script files only.

EXECUTE

This will be used to execute stored subprograms or packaged subprograms.

Syntax:

Execute or exec <subprogram_name>

Ex:

SQL> exec sample_proc

SPOOL

This will record the data when you spool on, upto when you say spool off.

Syntax:

Spool on | off | out | <file_name>

Ex:

SQL> spool on

SQL> select * from dept;

DEPTNO DNAME LOC

--------- -------------- ----------

10 ACCOUNTING NEW YORK

20 RESEARCH DALLAS

30 SALES CHICAGO

40 OPERATIONS BOSTON

SQL> spool off

SQL> ed on.lst

SQL> select * from dept;

DEPTNO DNAME LOC

--------- -------------- ----------

10 ACCOUNTING NEW YORK

20 RESEARCH DALLAS

30 SALES CHICAGO

40 OPERATIONS BOSTON

SQL> spool off

LIST

This will give the current SQL statement.

Syntax:

List or li [start_line_number] [end_line_number]

Ex:

SQL> select

2 *

3 from

4 dept;

SQL> list

1 select

2 *

3 from

4* dept

SQL> list 1

1* select

SQL> list 3

3* from

SQL> list 1 3

1 select

2 *

3* from

INPUT

This will insert the new line to the current SQL statement.

Syntax: Input or in <string>

Ex:

SQL> select *

SQL> list

1* select *

SQL> input from dept

SQL> list

1 select *

2* from dept

APPEND

This will adds a new string to the existing string in the SQL statement without any space.

Syntax:

Append or app <string>

Ex:

SQL> select *

SQL> list

1* select *

SQL> append from dept

1* select * from dept

SQL> list

1* select * from dept

DELETE

This will delete the current SQL statement lines.

Syntax:

Delete or del <start_line_number> [<end_line_number>]

Ex:

SQL> select

2 *

3 from

4 dept

5 where

6 deptno

7 >10;

SQL> list

1 select

2 *

3 from

4 dept

5 where

6 deptno

7* >10

SQL> del 1

SQL> list

1 *

2 from

3 dept

4 where

5 deptno

6* >10

SQL> del 2

SQL> list

1 *

2 dept

3 where

4 deptno

5* >10

SQL> del 2 4

SQL> list

1 *

2* >10

SQL> del

SQL> list

1 *

VARIABLE

This will be used to declare a variable.

Syntax:

Variable or var <variable_name> <variable_type>

Ex:

SQL> var dept_name varchar(15)

SQL> select dname into dept_name from dept where deptno = 10;

PRINT

This will be used to print the output of the variables that will be declared at SQL level.

Syntax:

Print <variable_name>

Ex:

SQL> print dept_name

DEPT_NAME

--------------

ACCOUNTING

IMPORTANT QUERIES

To find the nth row of a table

SQL> Select *from emp where rowid = (select max(rowid) from emp where rownum

<= 4);

SQL> Select *from emp where rownum <= 4 minus select *from emp where rownum

<= 3;

To find duplicate rows

SQL> Select *from emp where rowid in (select max(rowid) from emp group by

empno, ename, mgr, job, hiredate, comm, deptno, sal);

SQL> Select empno,ename,sal,job,hiredate,comm , count(*) from emp group by

empno,ename,sal,job,hiredate,comm having count(*) >=1;

To delete duplicate rows

SQL> Delete emp where rowid in (select max(rowid) from emp group by

empno,ename,mgr,job,hiredate,sal,comm,deptno);

To find the count of duplicate rows

SQL> Select ename, count(*) from emp group by ename having count(*) >= 1;

How to display alternative rows in a table?

SQL> select *from emp where (rowid,0) in (select rowid,mod(rownum,2) from emp);

Getting employee details of each department who is drawing maximum sal?

SQL> select *from emp where (deptno,sal) in

( select deptno,max(sal) from emp group by deptno);

How to get number of employees in each department , in which department is having more than 2500 employees?

SQL> Select deptno,count(*) from emp group by deptno having count(*) >2500;

To reset the time to the beginning of the day

SQ SQL> Select to_char(trunc(sysdate),’dd-mon-yyyy hh:mi:ss am’) from dual;

To find nth maximum sal

SQL> Select *from emp where sal in (select max(sal) from (select *from emp order

by sal) where rownum <= 5);

Wednesday, 9 October 2013

INTRODUCTION To Oracle (SQl Queries)-II

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