Stands for Procedural Language

PL SQL BlockRemember : Declare is optional and only required when variables need to be declared.. Whatever value user will enter here will be assign to variable name ‘ ‘ is used in cas

PL/SQL

Why PL SQL ?

 PL/SQL stands for Procedural Language/SQL.

 PL/SQL extends SQL by adding constructs found in

procedural languages like procedures, loops, variables, objects etc.

 Resulting a structural language that is more powerful than SQL

PL SQL, Is there any Advantage ?

 In case of SQL to send 3 queries we will need three network trips between client and server.

 In PL-SQL we bundle any number of queries in a block and in single network trip task is done.

SQL Query1

SQL Query2

SQL Query3

Client

Server

SQL Query1

SQL Query2

SQL Query3

Client Server

PL-SQL Block

Language features

 Supports constructs like any other 4th generation language:

 Variables and Data types

 Loops and Control statements

 Procedures and Functions

PL SQL Block

Remember :

Declare is optional and only required when variables need to be declared Exception is optional and required when Error/Exception handling is done Begin and End are mandatory as all logic and queries are written inside it.

Declare

Begin

Exception

End;

PL SQL program- Sample I

BEGIN

Insert into Dept values(70,’HR’,’Pune’);

Insert into Dept values(80,’PSD’,’Mumbai’);

Insert into Dept values(90,’ESG’,’Pune’);

END;

This program will insert three records at the same time in the table dept.

V_sum := v_num1 + v_num2 ;

Dbms_Output.Put_Line (‘The Sum of number is :’ || v_sum); END;

Save , Edit and Execute program

 Type your program in SQL * plus

 To save : Save <File Name>

Program is saved in the bin directory to save in other folder give complete path Eg: Save ‘C:\ESG\FirstPrg.sql’

 To make changes:

Edit <File Name>

To edit program saved in folder other then bin

 IF , ELSE , ELSIF , END IF

Cont

 Assignment operator: In PL SQL assignment operator is

 Important operators in PL SQL

 Line ends with operator: ;

 To join two strings: ||

Whatever value user will enter

here will be assign to variable

num1

Enter a value for Number1:

Whatever value user will enter

here will be assign to variable

name

‘ ‘ is used in case if entered data is not numeric

Enter a value for Name:

Display value : Examples

else values are not displayed.

Display value : Examples

 Select syntax is different then SQL , it contains INTO clause.

 If Select query can return more then one rows then you should

always use cursors

Select Syntax for a Single Row

Query.

 Select column1, column2

INTO Variable1,Variable2 From Table Name

Where condition …

 The only change is as many columns you want to get from the query you need to declare that many variables and use INTO clause

 All other parts of query are unchanged

 If Where condition here is such that query will return multiple records then CURSOR should be used Without that it will give error

language like Japenese , chinese etc

Number of characters it can store depend on language

To store multi byte variable length character data Its same as Varchar2 only difference is it is used to store characters of different language like Japenese , chinese etc

Number of characters it can store depend on language

Variable Declaration in PL SQL

 Variables are always declared in DECLARE section of the program

 Variable Name <Data Type>

 Various way to declare them

v_empno Number;

V_ename varchar2;

v_job Char(10);

Variable Declaration in PL SQL

 Dynamic and preferred way to declare a variable

Variable Name TableName.ColName%Type

v_empno Emp.Empno%Type;

V_ename Emp.Ename%Type;

v_deptno Dept.Deptno%Type;

 Advantages of declaring in above way

 Variable will always have same datatype as column

 Any change in column will change the type of variable also, so

we need not have to change and recompile the program to run

Variable Declaration in PL SQL

Variable Name TableName%RowType

v_emp Emp%RowType;

 Advantages of declaring in above way.

 Variable will become like a structure variable in C (i.e v_emp will have same structure like Emp Table) and you can refer to individual element as follows:

v_emp.empno v_emp.ename v_emp.sal

Variable Declaration in PL SQL

 Type : You can also make your own type in program and use in the declare section to declare variable

Type t_name is Varchar2(50);

now you can make variable of this type

v_name and v_name2 both will become varchar2(50)

 Note here that for one IF we only need one END IF;

 No END IF is required for ELSIF i.e for one set of IF condition only one END IF; is required

Conditional Statements

 CASE : This is available from ORACLE 8i onwards only , not in ORACLE 8 and version prior to that

CASE WHEN <Variable> = <Value1> Then

 Exit when is required to give the condition to end the loop

 It is pre tested as condition is checked first and then code is executed

TYPES OF LOOPS

 Simple Loop

Loop

Exit When i = 10dbms_output.put_line (i);End Loop;

Pre Tested

 Exit when is required to give the condition to end the loop

 It is post tested as condition is checked after the code is executed

TYPES OF LOOPS

 Simple Loop

Loop

dbms_output.put_line (i);Exit When i = 10

End Loop;

Post Tested

 While is required for condition to end the Loop

 This is also pre tested

 This Loop will execute the given code 100 times for i = 100 to 1

 This is reverse i.e from last value to first value

Looping over results of a query using

FETCH

existing rows

FOUND?

FETCH if rows

Explicit Cursor Attributes

Obtain status information about a cursor.

Attribute Type Description

%ISOPEN Boolean Evaluates to TRUE if the cursor

is open.

%NOTFOUND Boolean Evaluates to TRUE if the most

recent fetch does not return a row.

%FOUND Boolean Evaluates to TRUE if the most

recent fetch returns a row;

complement of %NOTFOUND

%ROWCOUNT Number Evaluates to the total number of

rows returned so far.

fetch c into num;

exit when c%NOTFOUND;

end loop;

close c;

end;

Printing Output

 You need to use a function in the DBMS_OUTPUT package

in order to print to the output

 The output is actually buffered

 If you want to see the output on the screen, you must type the following (before starting):

 set serveroutput on format wrapped size 1000000

 Then print using

 dbms_output put_line(your_string);

 dbms_output.put(your_string);

Trapping Oracle Server Errors

dbms_output.put_line('Too many!'); WHEN OTHERS THEN

dbms_output.put_line(SQLERRM);

end;

Functions and Procedures

block

can be called several times

CREATE [OR REPLACE] PROCEDURE

procedure_name

[(parameter1 [mode1] datatype1, parameter2 [mode2] datatype2, .)]

IS|AS

PL/SQL Block;

Creating Procedures

 Modes:

 IN: procedure must be called with a value for the parameter Value cannot be changed

 OUT: procedure must be called with a variable for the

parameter Changes to the parameter are seen by the user (i.e., call by reference)

 IN OUT: value can be sent, and changes to the parameter are seen by the user

 Default Mode is: IN

create or replace procedure

Errors in a Procedure

 If there are errors in the procedure definition, they will not

be shown

 To see the errors of a procedure called proc, type

 SHOW ERRORS PROCEDURE proc

in the SQLPLUS prompt

 For functions, type

 SHOW ERRORS FUNCTION fun_name

Creating a Function

supply a return type

CREATE [OR REPLACE] FUNCTION

function_name

[(parameter1 [mode1] datatype1,

parameter2 [mode2] datatype2,

[(parameter1 [mode1] datatype1,

parameter2 [mode2] datatype2,

)]

RETURN datatype

IS|AS

PL/SQL Block;

create or replace function

return 'You are great';

ELSIF rating >= 5 THEN

return 'Not bad';

return 'You are great';

ELSIF rating >= 5 THEN

return 'Not bad';

Trigger is like a procedure that is automatically invoked

by the DBMS in response to specified changes to data base

Trigger is like a ‘Daemon that monitors a data base, and is executed when the data base is modified in

a way that matches the event specification

A data base that has a set of associated triggers is called an active data base

Trigger Timings

Execute the trigger action before the triggering statement

Eliminate unnecessary processing of the triggering statement

AFTER triggers are used when you want the triggering statement

to complete before executing the trigger action

CREATE or REPLACE TRIGGER cs348

after INSERT ON weatherforecast

FOR EACH ROW

WHEN (:new.temp>= 60)

BEGIN

DBMS_OUTPUT.PUT_LINE(‘NICE WEATHER’); END cs348

/

Show error;

Triggers can be confusing

 Update table weatherforcast

T1 Fired

Before Update on weatherforcast

For each row

• What are the uses of triggers?

Flexible Management of integrity