Oracle PL/SQL(Advanced)

Topics 

• Sub Programs (Procedure and Functions)
• Stored Packages
• Database Triggers
• PL/SQL File I/O
• Collections
• Autonomous Transactions
• SQL Loader
Sub Programs in PL/SQL
• Subprograms are named PL/SQL blocks that can take Parameters and be invoked.
• PL/SQL has two types of subprograms called procedure and Function
• PL/SQL Programs can be stored in the database as stored
Procedure and can be invoked whenever required.
• Like Unnamed or anonymous PL/SQL block , subprograms have a declarative part, an executable part, and an optional Exception handling part.

Procedure
A procedure is a subprogram that perform a specific action, A procedure can be called from any PL/SQL program. Procedures can also be invoked from the SQL prompt
A procedure has two parts:
1 Specification.
2 Body.
Procedure specification begins with the key word Procedure Followed by the procedure name and an optional list of Arguments, enclosed within parenthesis.Procedure that take no parameters are
written without paranthesis .Procedure body begins with the Keyword IS or AS and ends with an
END followed by an optional procedure name.

The Procedure body has three parts:
1.Declarative Part Contains local declaration.
2.Executable Part contains statements, which are placed between The keyword BEGIN and Exception (or END).
3Exception Handling Part contains exception handlers, which are placed between the keyword Exception and End. This part is optional.

Syntax
Create [ OR REPLACE] PROCEDURE
( [mode] ,….)
IS AS
[Local declaration]
Begin
PL/SQL executable statements
[Exception
Exception handlers]
End [Procedure_Name];
Where mode indicates the type of the argument (Such as IN,OUT or IN OUT) and Pl/sql executable statements represents the PL/SQL Code, enclosed within Begin and End.
The OR REPLACE option is used in case the user wants to modify a previously stored procedure or function.

Example: Procedure
The Employee Number and the amount to be incremented is Passed as parameter
Create or Replace Procedure incr_proc (pempno number, amt number) IS
vsalary NUMBER;
Salary_miss Exception;
Begin
Select sal into vsalary from emp where empno= pempno;
If vsalary is NULL THEN
Raise salary_miss;
Else
Update emp set sal = sal + amt
Where empno= pempno;
End if;
Exception
When salary_miss then
Dbms_output.put_line (pempno' has salary as Null');
When no_data_found then
Dbms_output.put_line(pempno' No such Employee Number');
End incr_proc;
/

Calling a Procedure
A procedure is called as a PL/SQL statement. A procedure can be called from any PL/SQL program by giving their name followed by the parameters. To call the procedure named “incr_proc” from a block , the command is
incr_proc (v_empno, v_amount);
v_empno : Local variable storing the employee Number to be incremented.
v_amount : Local variable storing the amount to be incremented.
Procedure can also be invoked from the SQL prompt using the EXECUTE command
SQL> EXECUTE incr_proc(,);

Functions
A function is a subprogram that returns a value. A function must have a RETURN clause.
Functions and procedures have a similar structure , except that The function have a Return Clause.
Create [ OR Replace] Function
([mode],……..)
RETURN datatype IS
[Local Declaration]
BEGIN
PL/SQL executable statements
[EXCEPTION
exception handler]
END [FUNCATION_NAME];

Like a Procedure , a function has two parts:
• The Specification and the Body.
• The function specification begins with the Keyword FUNCTION And ends with the RETURN Clause, which specifies the datatype of the result value.
• The function body is exactly same as procedure body. Return Statement.
• Return Statement immediately returns control to the caller Environment. Execution then resumes with the statement following the subprogram call.
• A subprogram can contain several RETURN statements. Executing Any of them terminates the subprogram immediately. The Return Statement used in functions must contain an expression, which is Evaluated when the RETURN statement is executed . The resulting Value is assigned to the function identifier. Therefore a function must contain at least one RETURN statement.
• Note: RETURN statement can also be used in procedures. But it should not contain any expression. The statement simply returns control to the caller before normal End of the procedure is reached.

Example: Function
CREATE OR REPLACE FUNCTION review_func (pempno Number)
RETURN Number IS
vIncr emp.sal%type;
vNet emp.sal%type;
vsal emp.sal%type;
vcomm emp.comm%type;
vempno emp.empno%type;
BEGIN
SELECT empno,sal ,nvl(comm,0) INTO vempno,vsal,vcomm FROM emp
WHERE empno =pempno;
vNet:=vsal+vcomm;
If vsal<=3000 then vIncr:=0.20* vNet; Elsif vsal>3000 and vsal<=6000 then vIncr:=0.40* vNet ; End if; Return (vincr); End review_func ; / Calling of function named “review_func” from a pl/sql block. DECLARE Incr_sal number; BEGIN Incr_sal:= review_func(7698); Dbms_output.put_line (incr_sal); END; /

 Actual versus Formal Parameters
• The variables or expressions referenced in the parameter list of a subprogram call are actual parameters.
• The variables declared in a subprogram specification and referenced in the Subprogram body are formal parameters
• The following procedure call has two actual parameters pempno and amt. Incr_proc (pempno, amt)
• The following procedure declaration has two formal parameters named p_empno and amount
Create or replace procedure increment (p_empno Number ,amount Number) IS
----
--
BEGIN
--
--
END INCREMENT;

Argument Modes
Argument Modes are used to define the behavior of formal parameters There are 3 argument modes to be used with any subprograms
1. IN: The IN Parameter lets the user pass values to the called subprogram. Inside the subprogram, the IN Parameter acts like a constant, therefore, it cannot be Modified.
2 OUT: The Out Mode parameter lets the user return values to the calling block. Inside the subprogram, the Out Parameter acts like an uninitialized variable.
3 IN OUT : The IN OUT Parameter lets the user pass initial values to the called Subprogram and returns updated value to thecalling block.
The three parameters modes IN (the default), OUT, and IN OUT, can be used with any Subprograms. A procedure or function can change the value of the argument, which could be used for further processing.

Stored Packages
• A package is a database object that groups logically related PL/SQL objects.
• Packages encapsulate related procedures, functions,associated cursors and variables together as logical unit in the database.
• Packages are made of two components: The specifications and the body.
• The specification is the interface to applications and has declarative statements.
• The body of a package contains different procedures and functions.
• Packages are groups of procedures, functions, variables and SQL statements grouped into a single unit.
• The entire package is loaded into the memory when a procedure, within the package is called for the first time. This reduces the unnecessary disk I/O and network traffic.
Packages usually have two parts, a specification and a body.
Package specification
• The specification is the interface to the applications, it declares the types, variables, constants, exceptions, cursors and subprograms.
• The specification holds public declarations, which are visible to the applications.
• The scope of these declarations is local to your database schema and global to the package.So, the declared objects are accessible from your application and from anywhere in the package.
The Package Body
• The body fully defines cursors and subprograms, and so implements
• The body holds implementation details and private declarations, which are hidden from the application.
• The scope of these declarations is local to the package body.
• Unlike a package specification, the declarative part of a package body can contain subprogram bodies.

Main Advantages of Packages
• Better Performance
• Overloading
A package is created interactively with SQL*Plus
using the CREATE PACKAGE and CREATE PACKAGE BODY commands.
The syntax is:
Package Specification Syntax
CREATE[OR REPLACE] PACKAGE as
/*
DECLARATIONS OF GLOBAL VARIABLES AND CURSORS (IF ANY);
PROCEDURES AND FUNCTIONS;
*/
END [];
Package Body Syntax

CREATE [OR REPLACE] PACKAGE BODY AS
/*
PRIVATE TYPE AND OBJECT DECLARATION,
SUBPROGRAM BODIES;
*/
[BEGIN
--ACTION STATEMENTS;]
END [PKG-NAME];

Example of Package
CREATE OR REPLACE PACKAGE EMP_PACK AS
PROCEDURE EMP_PROC (PEMPNO IN EMP.EMPNO%TYPE);
FUNCTION INCR_FUNC (PEID NUMBER, amt NUMBER)
RETURN NUMBER;
END EMP_PACK;
/
CREATE OR REPLACE PACKAGE BODY EMP_PACK
AS
PROCEDURE EMP_PROC (PEMPNO IN EMP. EMPNO%TYPE)
IS
VTEMPNAME EMP.ENAME%TYPE;
VTESAL EMP.SAL%TYPE;
BEGIN
SELECT ENAME,SAL INTO VTEMPNAME,VTESAL FROM EMP WHERE

EMPNO=PEMPNO;
DBMS_OUTPUT.PUT_LINE (PEMPNO VTEMPNAMEVTESAL);
EXCEPTION
WHEN NO_DATA_FOUND THEN
DBMS_OUTPUT.PUT_LINE (PEMPNO 'NOT FOUND');
END EMP_PROC;
FUNCTION INCR_FUNC (PEID NUMBER, amt NUMBER)
RETURN NUMBER IS
vsalary NUMBER;
salary_miss EXCEPTION;
vtemp NUMBER;
BEGIN
SELECT sal INTO vsalary FROM emp WHERE empno=PEID;
IF vsalary IS NULL THEN
RAISE salary_miss;
/*If the vsalary is NULL an exception salary_miss is raised*/

ELSE
UPDATE emp set sal = sal+ amt where empno =PEID;
vtemp:=vsalary + amt;
RETURN (vtemp);
END IF;
EXCEPTION
WHEN salary_miss THEN
dbms_output.put_line (PEID ' has salary as NULL');
/* If the employee number is not found the exception NO_DATA FOUND
is raised*/
WHEN NO_DATA_FOUND THEN
dbms_output.put_line (PEID 'No such number');
END INCR_FUNC;
END EMP_PACK;
/
Calling a Procedure and Function of a Package
• Calling a Procedure of a Package
EXECUTE EMP_PACK.EMP_PROC(7499);
• Calling a Function of a Package
DECLARE
vsalary NUMBER;
BEGIN
vsalary:=EMP_PACK.INCR_FUNC(7499,100);
dbms_output.put_line (vsalary);
END;
/

Database Triggers
• A database trigger is a stored PL/SQL Program unit associated with a specific database table
• Unlike the stored procedures or functions which have to be explicitly invoked, these triggers implicitly gets fired (executed) Whenever the table is affected by anySQL operation
Parts of Trigger
--Trigger event
--Trigger Constraints (Optional)
--Trigger action

Trigger Events A triggering event or statement is the sql statement that Causes a trigger to be fired. A triggering event can be INSER,UPDATE or DELETE statement for a specific table
Trigger Restriction
Trigger restriction specifies a Boolean expression that must be True for a Trigger to fire. The Trigger action is not executed if the trigger restriction evaluates to FALSE. A trigger restriction is an option available for trigger that are fired for each row. Its function is to conditionally control the execution of the trigger A trigger restriction is specified using a WHEN clause.
Trigger Action
A trigger action is the procedure (PL/SQL block) that contain the SQL statements and PLSQL Code to be executed when a triggering Statement is issued and the trigger restriction evaluates to True

Syntax
Create [or Replace] TRIGGER
BEFORE AFTER INSTEAD OF
DELETE [OR] INSERT [OR] UPDATE [ OF [, …]]
ON
[REFERENCING [OLD [AS] ] [NEW [AS] ]]
[FOR EACH ROW [ WHEN ]]
BEGIN
---
/* PL/SQL Block */
----
END;
Description of Syntax of Database Trigger

Before Option: Oracle Fires the trigger before modifying each row affected by The triggering statement
After Option: Oracle fires the trigger after modifying each row affected by the triggering statement
Instead of Option: Oracle fires the trigger for each row , to do something else Instead of performing the action that executed the trigger.
WHEN Specifies the trigger restriction . This condition has to be satisfied to fire trigger. The condition can be specified for the ROW TRIGGER.

Statement Level Trigger:
Statement level trigger executes once for each transaction. For example if a single Transaction inserted 1000 rows into the EMP table, then a statement level trigger on that table would only be executed once.
Example:
To create a trigger for the EMP Table,
which makes the entry in the Ename column in Upper case
Create or replace trigger upper_trig1
Before insert or update of ename on emp for each row
Begin
:new.ename:=upper(:new.ename);
End;
/
RAISE_APPLICATION_ERROR
The raise application error is a built in Oracle Procedure which lets user issue the user defined error messages Range varies from (-20000 to -20999)
CREATE OR REPLACE TRIGGER Test_Trig BEFORE INSERT on emp FOR EACH ROW
BEGIN
IF inserting then
IF :NEW.sal=1500 then
RAISE_APPLICATION_ERROR(-20231,'Insertion Not Allowed');
END IF;
END IF;
END;
/

Instead of Trigger tells oracle what to do instead of performing the action that executed the trigger
• Except instead of trigger , all trigger can be used only on tables. Instead of triggers can be used only on view
Example
• View Create
create or replace view v_instead1 as
select empno,ename,emp.deptno,job,sal,dname,loc from emp,dept where emp.deptno= dept.deptno
• Trigger Create
create or replace trigger Tv_instead1 instead of delete on v_instead1 for each row begin
delete from emp where deptno=:old.deptno;
delete from dept where deptno=:old.deptno;
end;

PL/SQL File I/O (Input/Output)

File I/O is done through the supplied package UTL_FILE.
• The Oracle 8i Server adds file Input/Output capabilities to PL/SQL.
• This is done through the supplied package UTL_FILE.
• This package has some procedures and functions which add power to interact with a file.
• The file I/O capabilities are similar to those of the standard operating system stream file I/O (OPEN,GET,PUT,CLOSE), similar to the C programming file functions with some limitations.
• For example, you call the FOPEN function to return a file handle, which you then use in subsequent calls to GET_LINE or PUT to perform stream I/O to a file.
•After performing I/O on the file FCLOSE can be used to close the file.

Syntax and use of the UTL_FILE package Functions and Procedures:
1. FUNCTION FOPEN
FUNCTION FOPEN (LOCATION, FILENAME, OPEN_MODE)
RETURN UTL_FILE.FILE_TYPE;
LOCATION is the operating system-specific string that specifies the directory or area in which to open the file
FILENAME is the name of the file, including extension, without any directory information.
OPEN_MODE is a string that specifies how the file is to be opened.
Options allowed are “R” for Read, “W” for Write and “A” for Append.
Function FOPEN returns a file handle that is used in subsequent file
Operations.
Example:
V_FILENAME:=UTL_FILE.FOPEN(P_FILEDIR, P_FILENAME, ‘R’);

2. FUNCTION IS_OPEN
FUNCTION IS_OPEN (FILE)
RETURN BOOLEAN;
where
FILE is the value returned by FOPEN.
Function IS_OPEN tests a file handle to determine if it identifies an open
file.
Example:
BEGIN
IF UTL_FILE.IS_OPEN (‘P_FILE’) THEN

….
….
END IF;
END;

3. PROCEDURE FCLOSE
PROCEDURE FCLOSE (FILE) where FILE is the value returned by an FOPEN operation. PROCEDURE FCLOSE closes the open file identified by FILE.
Example:
UTL_FILE.FCLOSE(V_FILEHANDLE);

4. PROCEDURE GET_LINE
PROCEDURE GET_LINE (FILE, BUFFER);
where FILE is the value returned by an FOPEN operation. BUFFER holds the read text.

5. PROCEDURE GET_LINE reads a line of text from the open file identified by FILE and places the text in the output BUFFER.
Example:
UTL_FILE.GET_LINE (V_FILEHANDLE, V_NEWLINE);

6. PROCEDURE PUT_LINE
PROCEDURE PUT_LINE (FILE, BUFFER);
where FILE is the value returned by an FOPEN operation. BUFFER is the text to write.
PROCEDURE PUT_LINE writes text string BUFFER to the file identified by FILE, then writes a line terminator
Example:
UTL_FILE.PUT_LINE (V_FILEHANDLE, ‘ROLLNO NAME SUBJECT ’);
UTL_FILE.PUT_LINE (V_FILEHANDLE, ‘--------- ----- ------ ’);
The file will be written with the following format:
ROLLNO NAME SUBJECT
--------- ---- ------

Collections

• Nested Tables
• VARYING Arrays (VARRAY)

Nested Tables
A nested tables is useful for data models requiring referential integrity and is suitable for master-detail and one to many relationships. A nested table is a database table which stores data in it, that cannot be
A Nested Table can be included in a table definition as one of the columns. That is why, they are known as Nested Tables. Nested Tables can be manipulated directly using SQL.

To create a nested table the syntax is as follows:
CREATE TYPE TABLE_NAME IS TABLE OF TABLE_TYPE [NOT NULL];
where:
TABLE_NAME The name of new type ,TABLE_TYPE The type of each element in a nested table. It can be
built-in type, a user defined type or a reference to object type.
Example:
CREATE TYPE BOOKS_TYPE AS OBJECT
(BOOK_NO NUMBER (4),
BOOK_TITLE VARCHAR (20),
AUTHOR VARCHAR2(20));
/
Type created.
CREATE TYPE BOOKS AS TABLE OF BOOKS_TYPE;
/
Type created.

Example:
CREATE TABLE STUDENT (
STUDENT_NO NUMBER(4) NOT NULL,
STUDENT_NAME VARCHAR2(25),
BOOKS_ISSUED BOOKS )
NESTED TABLE BOOKS_ISSUED STORE AS BOOK_TABLE;
Table created.
Inserting Records
INSERT INTO STUDENT VALUES
(1001, 'AMIT KUMAR',
BOOKS (BOOKS_TYPE(3211, 'ORACLE 8 UNLEASHED', 'KAIT'),
BOOKS_TYPE(3922, 'PL/SQL PROG','J J')));
accessed directly.

Update is used to modify the store table
• The Operator allows nested tables to be manipulated using DML when it is stored in a table
• The table takes the sub query as argument and returns the Nested table to be used in DML.
• The Sub Query must return single nested columns
Example:
UPDATE THE (SELECT BOOKS_ISSUED FROM STUDENT WHERE
STUDENT_NO=1001)
SET BOOK_TITLE = 'ORACLE UNLEASHED'
WHERE BOOK_NO=3211;
Inserting records in nested Table
Example:
Insert into the (select books_issued from student where student_no=1001) values (books_type(5111, 'Visual Basic', 'Ken'));

Selecting a records from the Nested Table
Example:
select * FROM THE (SELECT BOOKS_ISSUED FROM STUDENT WHERE STUDENT_NO=1001) WHERE BOOK_NO=3211
/
Deleting a records from the Nested Table
For deleting a row from the nested table using the condition from the nested table
DELETE FROM THE (SELECT BOOKS_ISSUED FROM STUDENT WHERE
STUDENT_NO=1001) WHERE BOOK_NO=3211;

VARRAYS

Varray is a datatype similar to an array in C or PASCAL. Elements are inserted into a VARRAY, starting at index 1 up to the maximum lengthdeclared in the VARRAY type.

A VARRAY has the following:
• COUNT Current Number of elements
• LIMIT Maximum number of elements the VARRAY can contain. The LIMIT is user defined.
Each element of the array has the position indicated by an index which can range from one to the COUNT value. A VARRAY can be stored in a database column. A VARRAY can only be manipulated as a whole. Individual elements of stored VARRAYS cannot be modified.
Creating VARRAYs
Example:
CREATE TYPE BOOKS_TYPE1 AS OBJECT
(BOOK_NO NUMBER (4),
BOOK_TITLE VARCHAR (20),
AUTHOR VARCHAR2(20));
/
Type created.
CREATE OR REPLACE TYPE BOOKS_ARRAY AS VARRAY(10)
OF BOOKS_TYPE1;
/
Type created.
CREATE TABLE STUDENTS1(
STUDENT_NO NUMBER(4),
BOOKS_ISSUED BOOKS_ARRAY);
Table created.

Inserting Rows
The values can be inserted in a VARRAY as a whole, we can insert rows Into the table using the constructor as follows:
INSERT INTO STUDENTS1
VALUES
(2355, BOOKS_ARRAY(
BOOKS_TYPE1(1020,'ORACLE BEGINNERS', 'ORACLE PRESS'),
BOOKS_TYPE1(1111,'TUNING ORACLE','CONEY')));
This row contains a VARRAY BOOKS_ARRAY having two elements

Updating Rows
The VARRAYs can be updated as a whole. Individual elements cannot be accessed.
UPDATE STUDENTS1
SET BOOKS_ISSUED=BOOKS_ARRAY(
BOOKS_TYPE1(1020,'ORACLE BEGINNERS','ORACLE PRESS'))
WHERE STUDENT_NO=2355;
The row for STUDENT_NO 2355, will have only one element in the VARRAY column.

To modify a stored VARRY, it has to be selected into a PLSQL variable and then inserted back into the table .
The Technique is as below:
Note:
LIST_OF_BOOKS.COUNT gives the number of elements in the VARRAY
LIST_OF_BOOK.EXTEND appends one element ot the array i.e increase the array limit by 1
Example
DECLARE
LIST_OF_BOOKS BOOKS_ARRAY;
BEGIN
SELECT BOOKS_ISSUED INTO LIST_OF_BOOKS
FROM STUDENTS1 WHERE STUDENT_NO=2355;
DBMS_OUTPUT.PUT_LINE('NO OF BOOKS ISSUED' TO_CHAR(LIST_OF_BOOKS.COUNT));
DBMS_OUTPUT.PUT_LINE('ARRAY LIMIT' LIST_OF_BOOKS.LIMIT);
LIST_OF_BOOKS.EXTEND;
LIST_OF_BOOKS(LIST_OF_BOOKS.COUNT):=BOOKS_TYPE(2334,'DBA HANDBOOK','KEVIN');
UPDATE STUDENTS1 SET BOOKS_ISSUED=LIST_OF_BOOKS WHERE STUDENT_NO=2355;
COMMIT;
END;/

Autonomous Transactions
An Autonomous Transaction (AT) is an independent transaction started by another Transaction, The main transaction (MT). At the time of execution it lets you suspend the main transaction, do SQL Operation, Commit, or rollback those operation , then resume the main transaction. It always Executes with in an autonomous scope.
An autonomous Block is a routine marked with the:PRAGMA AUTONOMOUS_TRANSACTION

Example of Autonomous Transaction: Main Transaction
CREATE OR REPLACE Procedure PROC1_TRAN is
EMP_ID NUMBER:=7499;
BEGIN
UPDATE EMP SET SAL =SAL+100
WHERE EMPNO=EMP_ID;
PROC2_TRAN(EMP_ID);
DELETE FROM EMP
WHERE EMPNO=EMP_ID;
ROLLBACK;
END;
/
Autonomous Transaction
CREATE OR REPLACE Procedure PROC2_TRAN(P_EMP_ID NUMBER) is
PRAGMA AUTONOMOUS_TRANSACTION;
DEPT_ID NUMBER;
BEGIN
SELECT DEPTNO INTO DEPT_ID FROM EMP WHERE EMPNO=P_EMP_ID;
UPDATE DEPT SET DNAME='ACCOUNTING1'
WHERE DEPTNO=30;
COMMIT;
END;
/
SQL loader
This tool is used to move the data from Non –oracle standard source into the oracle Database Using sql loader a user can Load data from multiple data files Two types on input have to be provided to SQL*Loader.
The data file containing the actual data The control file containing the specification which drive the sql*loader session

SQL Loader generates three files
The log file (Summary of the execution of the Load)
The bad File (Rejected by Oracle)
The discard File (Doesn't meet the condition)

Create a Data File EMPLOYEE.TXT with following contents :
3000,HARPREET,ENGG,10000
3001,PREET1, ,20000
Create a Control File TEST.CTL with following contents :
LOAD DATA
INFILE 'EMPLOYEE.TXT'
APPEND
INTO TABLE EMP
WHEN JOB != ' '
Fields Terminated By ","
(
EMPNO
,ENAME
,JOB
,SAL
)
Calling a Control File TEST.CTL which in turn refers to EMPLOYEE.TXT file for Data are:
SQLLDR CONTROL=TEST.CTL

Oracle PL/SQL (Fundamentals)

Oracle PL/SQL (Fundamentals)

• PL/SQL
• Advantages of PL/SQL
• PL/SQL Block Structure
• Fundamentals of PLSQL
• Variables and Constants
• Bind Variables
• Built in Functions
• Conditional and Iterative Control
• Sql within PL/SQL
• Composite Datatypes (PL/SQL Records and PLSQL Tables)
• Cursors
• Exceptions
------------------------------------------------------------------------------------------------------------------------
• PL/SQL is the procedural extension to the non-procedural SQL
• Combines data manipulation of SQL and procedural power of standard procedural languages.
• Supports sub-programming features such as Procedures and Functions.

The Advantages of PL/SQL
• Support for SQL
• Block Structure
• Control Structures
• Better Performance
• Higher Productivity

PL/SQL Block Structure
Anonymous Blocks
Anonymous block is block without a name. These blocks are declared at the point in an application where they are to be run, and passed to the PL/SQL engine for execution at run-time.

The structure anonymous block is as follows:
DECLARE
BEGIN
EXCEPTION
END;

Fundamentals of PL/SQL
• Character Set
• Reserved Words
• Lexical Units
• Delimiters
• Identifiers
• Literals

Variables and Constants 
• Variables are used to store the result of a query or calculation.
• Variables must be declared before use.
• DEFAULT reserve word is used to initialize variables and constants.
• Variables can also be declared using the row attributes of a table %ROWTYPE and %TYPE.

Declaring Variables and Constants
• Variables are declared in the DECLARE section of the PL/SQL block.
• Declaration involves the name of the variable followed by its data type.
• All statements must end with a semicolon.
• Initial values can also be assigned to a variable at the time of declaration.
• To assign a value to a variable, the assignment operator := is used.
• They can also specify initial value and specify NOT NULL constraints.

Using DEFAULT
The reserved word DEFAULT can be used instead of the assignment operator to initialize variables and constants. For e.g.., the declarations
DEPTNO1 NUMBER (4):=40;
PIN_CODE1 CONSTANT NUMBER (6):= 110005;
can be rewritten as follows:
DEPTNO1 NUMBER (4) DEFAULT 40;
PIN_CODE1 CONSTANT NUMBER (6) DEFAULT 110005;

Using %TYPE 
To avoid type and size conflict between a variable and the column of a table, the attribute %TYPE is used. Advantage of this method of defining a variable is that, whenever the type and/or size of a column in the table is changed, it is automatically reflected in the variable declaration.
TMP_NAME EMP.ENAME%TYPE;
Here, the variable TMP_NAME will be of the same size and type as that of the same ename column of emp table.

Using %ROWTYPE
The %ROWTYPE attribute provides a record type that represents a row in a table. The record can store an entire row of data selected from the table. In case, variables for the entire row of a table need to declared, then instead of declaring them individually, the attribute %ROWTYPE is used:
EMP_ROW_VAR1 EMP%ROWTYPE;
Here, the variable EMP_ROW_VAR1 will be a composite variable, consisting of the column names of the table as its members. To refer to a specific Variable, say sal, the following syntax will be used:
EMP_ROW_VAR1.SAL:= 5500;

Scope and Visibility of a Variable
• The scope of a variable is the portion of the program in which the variable can be accessed.
• The visibility of a variable is the portion of the program where the variable can be accessed without having to qualify the reference.

Bind Variables
• A bind variable is a variable that you declare in a host environment.
• Bind variables can be used to pass run-time values, either number or character, into or out of one or more PL/SQL programs.
• The PL/SQL programs use bind variables as they would use any other variable.
Creating Bind Variables
• VARIABLE return_code NUMBER
• VARIABLE return_msg VARCHAR2(33)
• VARIABLE RESULT NUMBER

Displaying Bind Variables
To display the current value of bind variables in the SQL*Plus environment,use the PRINT command.
An example of using a host variable in a PL/SQL block:
BEGIN
SELECT (SAL*12) + NVL (COMM,0) INTO :RESULT
FROM emp WHERE empno =7369;
END;
/
PRINT RESULT:
To reference a bind variable in PL/SQL, you must prefix its name with a colon(:) .

Built-in-Functions
PL/SQL provides many powerful functions to enable easy data manipulation.
• The built-in-functions fall into the following categories:
• Error reporting Functions.
• Single-row number Functions.
• Single-row character Functions.
• Datatype conversion Functions.
• Date Functions.

Conditional and Iterative Control: The conditional control available with PL/SQL are
• IF THEN-ELSE Statement
The types of loops available with PL/SQL are:
• LOOP-END LOOP
• FOR-LOOP
• WHILE-LOOP

IF-THEN-ELSE statement
The IF clause can be used for the conditional processing of statements. If the condition specified after the IF clause evaluates to true, the statements following the THEN clause are executed until one of the following is encountered: ELSIF,ELSE or END IF.
The syntax for an IF-THEN-ELSE statement is
IF THEN
[ELSIF THEN
]
ELSE
END IF;

ELSE Clause
The ELSE clauses is optional. It should always be attached to IF clause.
Example
IF trans_type=‘CR’ THEN
UPDATE accounts SET bal=bal+credit WHERE………..
ELSE
UPDATE accounts SET bal=bal+credit WHERE………..
END IF;

ELSIF Clause 
The ELSIF clause is also optional as ELSE clause. If the first condition evaluates to FALSE the ELSIF tests another condition. An if statement can have any number of ELSIF clauses.
Example:
IF sales>5000 THEN
bonus:=1500;
ELSIF sales<3500 THEN
bonus:=500;
ELSE
bonus:=1000;
END IF;

Simple Loop (LOOP-ENDLOOP)
The syntax is:
LOOP
END LOOP;
Each time the flow of execution reaches the END LOOP statement, control is returned to the corresponding LOOP statement above it. This LOOP is endless without EXIT statement.

The EXIT Statement 
To control the termination of above mentioned loop EXIT statement is used. EXIT statement allows control to be passed to the next statement beyond END LOOP, thus ending the loop immediately.
Example:
LOOP
ctr:=ctr+1;
IF ctr =10 THEN
EXIT;
END IF;
END LOOP;

EXIT WHEN Statement
EXIT-WHEN statement allows a loop to complete conditionally. When the EXIT statement is encountered, the condition in the WHEN clause is evaluated. If the condition evaluates to TRUE, the loop completes and the control passes to the next statement after the loop.
The EXIT-WHEN statement replaces a simple If statement.
The syntax is:
EXIT [loop-label] [WHEN condition];
Example:
LOOP
ctr:=ctr+1;
EXIT WHEN ctr =10;
END LOOP;

FOR LOOP 
FOR loops iterate over a specified range of integers. The range is part of an iteration scheme, which is enclosed by the keywords FOR and LOOP.
The syntax is
FOR IN .. LOOP

END LOOP; is the name of variable whose value will be incremented/decremented automatically on each iteration of the loop.
The index variable has the following properties:
• It is of datatype NUMBER and need not be declared
• It’s Scope is only within the FOR loop.
• Within the FOR loop, the index variable can be referenced, but not modified.
and are integer expressions which determine the range of values for the control variable.
By default, the control variable begins with the value of and is Incremented by +1 on each iteration until is reached. The loop is terminated at the end of this iteration.
Example:
FOR ctr IN 1..20
LOOP
INSERT INTO temp values (ctr);
……….
……….
END LOOP:
NOTE: If ctr is required beyond the end of the loop, then it must be copied to a declared variable before the loop ends.

WHILE-LOOP
The WHILE loop tests the condition provided, and if evaluates to true, then the statements within the LOOP and END LOOP are executed. The loop continues as long as the condition is true.
The syntax is
WHILE LOOP

END LOOP;
Example
WHILE total<=2000 LOOP
………………..
SELECT sal into salary FROM emp WHERE
total := total+salary;
END LOOP;

SQL Within PL/SQL

• DML in PL/SQL
• The INTO Clause. Points to remember while using SQL commands within PL/SQL
• SELECT statements which do not return a single row will cause an exception to be raised.
• DML commands can process multiple rows.
DML in PL/SQL
The allowable DML statements are SELECT, INSERT, UPDATE and DELETE.The INTO Clause
The INTO clause is used with SELECT, to store values from the table into variables.

Writing PL/SQL Code
PL/SQL Code is written using any text editor. The PL/SQL program is compiled and executed using the command @.
• Inserting Comments in PL/SQL Program Comments can be placed in PL/SQL with a double minus(-) preceding
the comment or within/*….*/.
• dbms_output.put_line( )
The procedure dbms_output.put_line will produce the output on the screen. It accepts only one argument.
Hence, the different variables are concatenated with double pipe() symbol.
To enable the server output, the SET SERVER OUTPUT ON command must be given at the SQL*Plus prompt, prior to the execution of the dbms_output.put_line function.

Example: A.
Write a PL/SQL code to update salary of employees number is 7499 to 5000 if salary is less than 5000.
DECLARE
x NUMBER;
BEGIN
SELECT sal INTO x FROM emp WHERE empno =7499;
IF x<5000 THEN
UPDATE emp SET sal=5000 WHERE empno=7499;
END IF;
END;
/
Example: B.
Write a PL/SQL code to insert all the details of employee no 7499 to a new table emp1 which has same structure as emp table.
DECLARE
v_newrec emp%ROWTYPE;
BEGIN
SELECT * into v_newrec FROM emp WHERE empno=7499;
INSERT into emp1
VALUES (v_newrec.empno, v_newrec.ename, v_newrec.job,
v_newrec.mgr, v_newrec.hiredate, v_newrec.sal, v_newrec.comm,
v_newrec.deptno);
END;
/
Composite Datatypes
PL/SQL Records
• PL/SQL records provides a way to deal with separate but related variables as a unit.
• PL/SQL record is a variable that may contain a collection of separate values, each individually addressable.
• The record type has to be defined before its record can be declared.
• In case one of the record component is a record, then it is called a nested record.
The syntax for creating a record is
TYPE IS RECORD
({field-typevariable%TYPEtable.column%TYPE
table%ROWTYPE},{field-typevariable%TYPE
table.column%TYPEtable%ROWTYPE} ……);

PL/SQL Tables
• PL/SQL tables are modeled as database tables, but are actually not
• Primary keys can be associated with them to have array-like access to rows
• The size can be dynamically increased by adding more rows when required. However no rows can be deleted
• PL/SQL tables can have one column and a primary key, neither of which can be named
• Column can belong to any scalar type, but the primary key must
belong to BINARY_INTEGER
TYPEIS TABLE OF
[NOT NULL]
INDEX BY BINARY_INTEGER;

Example: PL/SQL Records
The following PL/SQL program displays the total salary which includes commission of empno 7369. It should also display employees name, his department details and his old and new salary.

Declare
TYPE Deptrec is record (dno dept.deptno%TYPE, vdname dept.dname %TYPE, vloc dept.loc%TYPE,
name emp.ename%TYPE, vsal emp.sal%TYPE, vcom emp.comm%TYPE, newsal emp.sal%TYPE);
dept_det deptrec;

BEGIN

SELECT ename, sal, comm, dept.deptno, dname, loc into dept_det.name,
dept_det.vsal, dept_det.vcom, dept_det.dno, dept_det.vdname, dept_det.
vloc FROM emp, dept
WHERE emp.deptno=dept.deptno and empno=7369;
dept_det.newsal:=dept_det.vsal+NVL(dept_det.vcom,0);
DBMS_OUTPUT.PUT_LINE
(dept_det.dnodept_det.vdnamedept_det.vloc dept_det.namedept_det.vsaldept_det.vcomdept_det.newsal);
END;
/

Examples: PL/SQL Tables
To load the employees names and salaries into PL/SQL tables and then display the contents of the table.

DECLARE
TYPE EMPNAMETYPE IS TABLE OF EMP.ENAME%TYPE NOT NULL
INDEX BY BINARY_INTEGER;
TYPE EMPSALTYPE IS TABLE OF EMP.SAL%TYPE
INDEX BY BINARY_INTEGER;
ENAMELIST EMPNAMETYPE;
SALARYLIST EMPSALTYPE;
SUBSCRIPT BINARY_INTEGER:=1;
CTR NUMBER:=1;
BEGIN
FOR EMPREC IN (SELECT ENAME, SAL FROM EMP) LOOP
ENAMELIST (SUBSCRIPT):=EMPREC.ENAME;
SALARYLIST(SUBSCRIPT):=EMPREC.SAL;
SUBSCRIPT:=SUBSCRIPT+1;
END LOOP;

WHILE ctr <subscript
LOOP
DBMS_OUTPUT.PUT_LINE (ENAMELIST(ctr));
DBMS_OUTPUT.PUT_LINE (SALARYLIST(ctr));
CTR:=CTR+1;
END LOOP;
END;
/

Cursors
Cursors: Oracle Uses work area called Private SQL areas to execute SQL Statements and store information. A Cursor is a PL/SQL construct that allows you to name these work areas, and to access their stored information
Types of Cursor
• Implicit Cursors
• Explicit Cursors
Implicit Cursor: Implicit Cursor are declared by PL/SQL implicitly for all DML Statements and for single row queries
Example: Select Statement issued directly within the BEGIN .. END part of a block opens up an implicit cursor.
Explicit Cursors : Declared and named by the programmer Explicit Cursors allow multiple rows to be processed from the query.

Implicit Cursor
DECLARE
v_x_sal number;
BEGIN
SELECT sal INTO v_x_sal FROM emp where empno=7499;
DBMS_OUTPUT.PUT_LINE(v_x_sal);
END;
/
Implicit Cursor has four attributes
• SQL%NOTFOUND
• SQL%FOUND
• SQL%ISOPEN
• SQL%ROWCOUNT

Explicit Cursors
Active Set: The Set of rows returned by a multiple row query Its Size is the number of rows that meets your search criteria Explicit cursor points to the current row in the active set. This allows your program to process the rows one at a time.
Explicit Cursors
Declaring a Cursor
• Cursor Name
• Structure of the Query
Syntax: CURSOR IS  : It includes most of the usual clauses, but INTO Clause is not allowed
Example:
DECLARE
CURSOR c1 is SELECT ename, deptno FROM emp WHERE sal>2100;
………………………………
BEGIN
………………………………
END;
Opening a Cursor
Here Query execution is done. After Opening the Cursor the rows returned by the query are available for fetching.
Syntax: Open ;
This statement is used within the executable section of the block. It also establishes an active set of the rows
Example:
OPEN c1;
The cursor will now point to the first row in the active set.

Retrieving Individual rows 
After the cursor is opened the current row is loaded Into variables. The current row is the row at which The cursor is currently pointing The retrieval of data into PL/SQL variable or host
Variable is done through FETCH statement
Syntax:
FETCH INTO ;
• For each column value returned by the query Associated with the cursor, there must be a
Corresponding variable in the INTO list.
• ALSO their Datatypes must be compatible

Example of Using Fetch Command
DECLARE
v_sal number;
CURSOR c1 is SELECT sal FROM emp WHERE job='CLERK';
BEGIN
OPEN C1;
LOOP
FETCH C1 into v_sal;
EXIT WHEN c1%NOTFOUND;
DBMS_OUTPUT.PUT_LINE (v_sal);
END LOOP;
CLOSE C1;
END;
/
CLOSING A CURSOR: It explicitly closes the cursor, allowing it to be Reopened , if required.
Syntax:
CLOSE
Example: CLOSE c1
Example of Using CLOSE
DECLARE
v_name emp.ename%TYPE;
CURSOR c1 is select ename from emp;
BEGIN
OPEN c1;
LOOP
FETCH c1 into v_name;
EXIT WHEN c1%NOTFOUND;
DBMS_OUTPUT.PUT_LINE(v_name);
END LOOP;
CLOSE C1;
END;
/
Explicit Cursor Attributes
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
%ROWCOUNT - NUMBER - Evaluates to the total number of rows returned so far

Cursor and Records
Process the rows of the active set by fetching values into a PL/SQL Record
DECLARE
CURSOR emp_cursor is Select empno,ename FROM emp;
Emp_record emp_cursor%rowtype;
BEGIN
OPEN emp_cursor;
LOOP
FETCH emp_cursor INTO emp_record;
EXIT WHEN emp_cursor%notfound;
DBMS_OUTPUT.PUT_LINE(emp_record.ename);
END LOOP;
CLOSE emp_cursor;
END;
/

Cursor FOR Loops 
Syntax:
FOR record_name IN cursor_name LOOP
statement1;
statement2;
. . .
END LOOP;
•The cursor FOR loop is a shortcut to process Explicit cursors
•Implicit Open,fetch,exit and close occurs
•The record is implicitly declared
Example: Cursor FOR Loop
DECLARE
CURSOR emp_cursor IS
SELECT ename,deptno FROM Emp;
BEGIN
FOR emp_record IN emp_cursor
LOOP
IF emp_record.deptno = 20 THEN
DBMS_OUTPUT.PUT_LINE ('Employee ' emp_record.ename
'works in the Research Dept.');
END IF;
END LOOP;
END;
/
Cursor For Loops Using Sub queries
• No need to declare the cursor
Example:
Begin
FOR emp_record in (SELECT ename, deptno from emp)
LOOP
IF emp_record.deptno =20 THEN
DBMS_OUTPUT.PUT_LINE ('Employee '
emp_record.ename ' works in the Research Dept. ');
END IF;
END LOOP;
END;
/
Difference between Implicit and Explicit Cursor
Implicit Cursors : Used for all DML Statements and Single row queries.
Explicit Cursors : Used for queries of zero, one or More rows.
Cursor with Parameters
Syntax:
CURSOR cursor_name(parameter_name datatype, )
IS
Select_statement;
• Pass parameter values to a cursor when the cursor is opened and the query is executed
• Open an explicit cursor several times with different active set each time
Open cursor_name(parameter_value , ……);
Example Cursor with Parameters
DECLARE
CURSOR c1(p1 number) is
Select empno,ename,sal,deptno from emp where deptno=p1;
Crec c1%rowtype;
Vdeptno number:=20;
BEGIN
OPEN c1(10);
LOOP
FETCH c1 into crec;
IF c1%FOUND THEN
IF crec.sal >5000 THEN
Dbms_output.put_line(crec.empno' 'crec.sal ' ' crec.deptno);
End if;
ELSE
Exit;
END IF;
END LOOP;
CLOSE C1;
OPEN C1(Vdeptno);
LOOP
FETCH c1 into crec;
IF c1%FOUND THEN
IF crec.sal >5000 then
Insert into emp1(empno,ename,sal,deptno) values (crec.empno,crec.ename,crec.sal,crec.deptno);
END IF;
ELSE
Exit;
END IF;
END LOOP;
CLOSE C1;
END;
/

The For Update Clause
Syntax:
SELECT …..
FROM ……
FOR UPDATE [OF column_reference][NOWAIT];
• For Update Clause can be used within the cursor query. This means that rows returned by the query are locked exclusively when the OPEN statement is processed. Since locks are released at the end of the transaction. Commit command should not be given across fetches from an explicit cursor if FOR UPDATE is used.
• The For Update clause is the last clause in a select statement, even after the ORDER BY.
• Lock only those records which are satisfied by condition.. • NOWAIT : Returns an Oracle error if the rows are locked by another session.

The WHERE CURRENT of clause
• This allows you to apply update and deletes to the row Currently being addressed , without the need to explicitly reference the ROWID.
• Must Include the FOR UPDATE clause in the cursor query So that the rows are locked on Open

Example : For Update and WHERE CURRENT of clause
DECLARE
Cursor c1 is SELECT empno, ename, dept.deptno,sal
FROM dept,emp where emp.deptno=dept.deptno
AND emp.deptno=20 FOR UPDATE OF sal NOWAIT;
BEGIN
FOR emp_record in c1
LOOP
IF emp_record.sal <5000 then
Update emp set sal= emp_record.sal*1.10
Where Current of c1;
END IF;
END LOOP;
END;
/
The slide example loops through each employee in Department 20 and checks whether the salary is Less than 5000. If the salary is less than 5000, the Salary is raised by 10%. The Where Current of Clause in the Update Statement refers to the currently fetched record.

Exceptions Handling in PL/SQL
• In PL/SQL, a warning or error condition is called an exception
• When an error occurs, an exception is raised, i.e. the normal execution stops and the control transfers to the exception handling part of the PL/SQL block.

• Exceptions can either be of two types:
1. Predefined Exceptions
2. User Defined Exceptions
Exceptions are identifiers in PL/SQL which may be ‘raised’ during the execution of a block to terminate its main body of actions. A block will always terminate when an exception is raised, but you may specify an ‘Exception Handler’ to perform final actions before the block terminates.
Predefined Exceptions 
• Predefined exceptions are internally defined by runtime system
• A predefined exceptions are raised implicitly Predefined exceptions are raised whenever PL/SQL program violates an ORACLE rule . Every ORACLE error has a number, but exceptions must be handled by name.

Exception Handlers
If any type of exception is raised, control is passed to the EXCEPTION section of the block in which the exception occurred. If the exception is not handled there, or of there is no EXCEPTION section at all, then the Block terminates with an unhandled exception, which may effect the enclosing environment. The same exception cannot be declared more than once in the same PL/SQL block.
The syntax of defining exception handler is WHEN THEN ;
Where ‘actions’ may be one or more PL/SQL or SQL statements, each Terminated by semi-colons.

Example Pre Defined Exceptions
DECLARE
vename emp.ename%TYPE;
vjob emp.job%TYPE;
BEGIN
SELECT ename, job INTO vename, vjob FROM emp WHERE hiredate
BETWEEN '01-JAN-97' AND '31-DEC-97';
DBMS_OUTPUT.PUT_LINE (vename' 'vjob);
EXCEPTION
WHEN NO_DATA_FOUND THEN
dbms_output.put_line ('No Employees hired in 97');
WHEN TOO_MANY_ROWS THEN
dbms_output.put_line ('More than one Manager has joined in 97');
END;
/
Some of the predefined exceptions are:
• CURSOR_ALREADY_OPEN
• DUP_VAL_ON_INDEX
• INVALID_CURSOR
• TOO_MANY_ERROR
• INVALID_NUMBER
• NO_DATA_FOUND
• ZERO_DIVIDE

When Others Exception
• Although the Exception section in the previous example would trap the two exception, specified other types of exception are ignored
• Rather than defining a separate handler for every exception type, When others exception handler is defined which handles all errors not already handled in the block
• When others exception handler should always be the last exception handler in the block.

When Other Exception Handler 
DECLARE
BEGIN
EXCEPTION
When no_data_found then
Dbms_output.put_line ('No employee hired in 97');
When too_many_rows then
Dbms_output.put_line ('More than one manager has joined in 97');
When others then
Dbms_output.put_line ('Error during execution of the block');
END;
/
When an exception has occurred, one wants to evaluate the associated error
Pl/sql provides two functions for this purpose 

SQLCODE: It returns the error number associated with the exception that has occurred.
SQLERRM: It returns character data. It returns the complete error message associated with the exception including the error number.

Example : SQLCODE And SQLERRM
DECLARE
Error_message varchar2(100);
Error_code Number;
BEGIN

EXCEPTION
When others then
Error_message:=substr(sqlerrm,1,100);
Error_code:=sqlcode;
Dbms_output.put_line (Error_message' ' Error_code);
END;
/

User Defined Exception
• User defined exceptions are declared and defined by the user.
• User defined exceptions must be raised explicitly using the Raise Statement.
Plsql allows to define user defined exception. Unlike predefined Exception, user defined exceptions must be declared and must be raised explicitly by Raise statements.
Declaring an Exception can be declared only in the declarative part of PL/SQL Block, subprograms, or package

Syntax of Declaring exception

Identifier EXCEPTION;
Note: Exception and variable declaration are similar. But an Exception is an error condition, not an object. Unlike variables, Exceptions cannot appear in assignment statements or SQL Statements

Example:
The following pieces of code illustrate the declaration and use of user defined exceptions.
DECLARE
------
OUT_OF_STOCK EXCEPTION;----User defined exception
QTY_ONHAND NUMBER(5);
BEGIN
------
IF QTY_ONHAND < 1 THEN
RAISE OUT_OF_STOCK; ----Raise the User Defined Exception
END IF;
-----
----
EXCEPTION
WHEN OUT_OF_STOCK THEN----Handle the User Defined Exception
/* Write the Exception Handling codes Here */
END;

How Exceptions are Raised
• Implicitly in case of Pre defined Exceptions
• Explicitly using a Raise command in Case of User Defined Exception.
Notes:
• Exception cannot be declared twice in the same block . However, Same exception can be declared in two different blocks
• Exceptions declared in a Block are considered local to that block and global to all its sub block. Because a block can reference only Local or global exceptions , enclosing blocks cannot reference
Exception declared in a sub block.

How Exceptions are Raised
• Implicitly in case of Pre defined Exceptions
• Explicitly using a Raise command in Case of User Defined Exception.
Notes:
• Exception cannot be declared twice in the same block . However, Same exception can be declared in two different blocks
• Exceptions declared in a Block are considered local to that block and global to all its sub block. Because a block can reference only Local or global exceptions , enclosing blocks cannot reference
Exception declared in a sub block.

Example A: Raising and Handling User Defined Exceptions
Declare
My_exception Exception;
-----
Begin
----------
Begin
---------------
----------------
Raise My_exception;
Exception
When My_Exception Then
---------
---------
End;
--
End;

Example B: Raising and Handling User Defined Exceptions
Declare
My_Exception1 Exception;
My_Exception2 Exception;
BEGIN
-----
BEGIN
----
IF THEN
RAISE MY_EXCEPTION2;
EXCEPTION
WHEN MY_EXCEPTION1 THEN
------
------
END;
-----
Exception
When MY_EXCEPTION2 THEN
----
---
END;
---</subscript