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PL/SQL
PL/SQLextends SQL by adding constructs found in procedural languages, resulting in a structural language that is more powerful than SQL
PL/SQLstands for Procedural Language/SQL
PL/SQLcombines the data manipulating power of SQL with the data processing
power of procedural languages.
PL/SQL Architecture
The PL/SQLcompilation and run-time system is a technology, not an independent product.
PL SQL Engine compiles and executes PL/SQLblocks and subprograms
The engine can be installed in an Oracle server or in an Oracle development tool such as Oracle Forms or Oracle Reports
PL/SQL Architecture
APPLICATION /Pro*(C/ C++/ COBOL)/Forms/ Reports
Host languageHost languageHost language
PL/SQLStatement Executor
Oracle Server
SQL Statement Executor
EmbeddedPL/SQLBLOCKDECLARE ProceduralBEGIN Procedural SQL Procedural SQLEND;
EmbeddedPL/SQLBLOCKDECLARE ProceduralBEGIN Procedural SQL Procedural SQLEND;
Front-end OR Back-end Application portion
!
Execution of a PL/SQL Block
PL/SQL Block
PL/SQLcode is grouped into structure called blocks.
PL/SQLblocks come in three types
• Anonymous procedure
• Named procedure
• Named function.
PL/SQL Blocks
An anonymous procedure is an unnamed procedure, it can't be called. It is placed where it is to be run, normally attached to a database trigger or application event.
A named procedure may be called, it may accept inbound parameters but won't explicitly return any value.
A named function may also be called, it may accept inbound parameters and will always return a value.
PL/SQL Block
• DECLARE Definition of any variables or objects that are used within the declared block.
• BEGIN Statements that make up the block.
• EXCEPTION All exception handlers.
• END;End of block marker.
For ExampleDECLARE x NUMBER;BEGIN
X := 15000;DBMS_OUTPUT.PUT_LINE
(‘The values for x is ’);DBMS_OUTPUT.PUT_LINE (X);
EXCEPTIONWHEN OTHERS THEN
DBMS_OUTPUT.PUT_LINE (‘Error Occurred’);
END;/
Execution of Blocks
There are three basic ways to execute PL/SQL Code
1. Cut and paste from notepad
2. Execute a text file using SQL*PLUS
SQL> @c:\samples\test.sql
3. Use SQL*PLUS EDIT command
Types of VariablesPL/SQL Variables:
1. Scalar (Char,Number,Varchar,Varchar2)2. Composite(PL-SQL Records)3. Reference (%Type,%RowType)4. LOB,CLOB,BFILE (large Objects) Ex to be
given
Types of Variables
• PL/SQL does not have input or output capability of its own
• You can reference substitution variables within a PL/SQL block with a preceding ampersand (&)
• SQL*Plus host(or bind)variables can be used to pass run time values out of the PL/SQL block back to the SQL*Plus environment
• Non-PL/SQL Variables: Bind variables
!@
Variable DeclarationsExamples
• DECLAREfirstName, lastName CHAR(20); -- illegal
• DECLAREEmp_No NUMBER NOT NULL := 10109;Total_Sal NUMBER(3,1);XYZ NUMBER(2,2) := 31.8;Salary NUMBER(9,2) := XYZ * 131;V_CHR2 VARCHAR2(12) :="JANUARY";TODAY_DATE := SYSDATE;TRUEFALSE BOOLEAN;
• DECLAREPI CONSTANT NUMBER(9,3) := 3.142; --Constants Declaration
• DECLARERec1 Emp%ROWTYPE; Emp –Table Name
Variable Assignment• PL/SQL Expressions consist of Variables, Constants, Literal,
and Function Calls.Syntax:
plsql_variable := plsq1_expression;
• Quick Notes : := (ASSIGNMENT) = (VALUE EQUALITY)The datatype on the left and right side of an assignment
must be the same or implicitly convertible to each other.N := '7' -- legal
Column or table references are not allowed on either side of the assignment operator (:=).
SCOTT.EMP.EMPNO := 1234;location := dept.loc; -- illegal.
Variable Assignment Examples
N1 := 5 * N2 * 0.7;B1 := TRUE;D1 := '11-JUN-97';C1 := NULL;N1 := SQRT( N2 ** 2 – 4 * N3 * N4);
Note: Nn is Number typeBn is BooleanCn is Char typeDn is Datetype
!
Scope of Variables and Constants
SCOPE refers to the visibility of identifiers at different points in the PL /SQL block
RULES:1. An identifier is visible in the block in which it is
declared and all its sub-blocks unless rule #2 applies.
2. if an identifier declared in an enclosing block is re-declared in a sub-block, the original identifier declared in the enclosing block is no longer visible in the sub-block However, the newly declared identifier has the rules of scope defined in rule #1. Ex to be Given
DBMS_OUTPUT.PUT_LINE
An Oracle-supplied packaged procedure
An alternative for displaying data from a PL/SQL block
Must be enabled in SQLPlus or iSQL*Plus with
SET SERVEROUTPUT ONDECLARE
V_1 Number(30) := 20;BEGIN
DBMS_OUTPUT.PUT_LINE (‘TEST RUN’ || V_1);END;/
Special Symbols/OperatorsSymbol
+
-
*
/
=
@
;
<>
!=
||
--
/*
*/
:=
Meaning
Addition operator
Subtraction
Multiplication
Division
Relational operator (compare)
Remote access indicator
Statement terminator
Relational operator (compare)
Relational operator (compare)
Concatenation Operator
Single line comment
Beginning of comment (multi-line)
End of comment (multi-line)
Assignment Operator
Interacting with Oracle Server
SQL Data Manipulation Language statement supportINSERT, UPDATE, DELETE, SELECT
Quick Notes:The full Oracle syntax is supported for these statements.A PL/SQL variable may be placed anywhere a construct may be legally placed.An identifier is first checked to see if it is a column in the database. If not, it is assumed to be a PL/SQL identifier.These statements may not appear as part of an expression
Example: INSERT
DECLARE my_Sal NUMBER(7, 2) := 3040.55; my_eName CHAR(10) := 'WANDA';
my_HireDate DATE := '08-Sep-88';BEGIN
INSERT INTO Emp (empNo, eName, Job,hireDate, Sal, deptNo)
VALUES (2741, my_eName, my_HireDate, my_Sal, 20);
END;
SQL in PL / SQL
Example: UPDATE
DECLARE
max _Allowed CONSTANT
NUMBER:= 5000;
BEGIN
UPDATE Emp SET Sal =
max_Allowed
WHERE empNo = 7934;
END;
SQL in PL / SQL
!
Example: DELETE
BEGIN
DELETE FROM Emp
WHERE deptNo = 10 ;
END;
SQL in PL / SQL
SELECTSyntax
SELECT col1, col2,.,. into var1,var2 FROM table name WHERE …
• Quick Notes:– A SELECT statement is the only DML that returns
data. You must provide a location for this data to be stored via the INTO clause.
– A SELECT...INTO statement must return exactly one row. Zero or multiple returned rows results in an error.
– For multi-row SELECT's use cursors (discussed later).
SQL in PL / SQL
Example: SELECT
DECLARE
part_Name Parts.name%TYPE;
num_In_Stock Parts.num%TYPE;
BEGIN
SELECT Name, Num INTO part_Name, num_In_Stock
FROM Parts WHERE part_Id = 624;
--manipulate the retrieved data here--
END;
SQL in PL / SQL
SQL in PL / SQLFunctional support
• within a SQL Statement:
– Numeric (e.g. SQRT, ROUND, POWER)
– Character (e.g. LENGTH, UPPER)
– Date (e.g. ADD_MONTHS, MONTHS_BETWEEN)
– Group (e.g. AVG, MAX, COUNT)
INSERT INTO emp (ename) VALUES (UPPER(ename)
• outside of a SQL Statement:x := SQRT(y);lastname := UPPER(lastname);agediff := MONTHS_ BETWEEN(bday1, bday2)/12;
Note: Most of the SQL functions are available except the group functions.
Transaction Processing• Definition
ROLLBACK
SAVEPOINT MARKER A
(ROLLBACK TO)
SAVEPOINT MARKER B
(ROLLBACK TO)
SAVEPOINT MARKER C
(ROLLBACK TO)
COMMIT
SyntaxSAVEPOINT < marker_name >;
ROLLBACK [WORK] TO [SAVEPOINT] < marker_name >;
Transaction ProcessingE.G.
BEGININSERT INTO temp(num,des)VALUES (1, 'row 1');
SAVEPOINT A;… …
INSERT INTO temp (num,des) VALUES (2, 'row 2');SAVEPOINT B;… …
INSERT INTO temp (num,des) VALUES (3, 'row 3');SAVEPOINT C;… … … ...
ROLLBACK TO SAVEPOINT B;
COMMIT;END;
Control Structures
• Conditional: IF statements
• Iterative: LOOP and EXIT statements
• Sequential: GOTO and NULL statements
T F
F
T
Condition Iteration Sequence
!
Conditional Control• Condition:
Logical Comparisons form the basis of conditional control in PL/SQL; the results of these comparisons are always either TRUE, FALSE or NULL.
• Quick Notes:– Anything compared with NULL results in a NULL
value.– A NULL in an expression evaluates to NULL(except
concatenation).– E.g..
5 + NULL -- evaluates to NULL'PL'||NULL||'/SQL' -- evaluates to PL/SQL
!
Conditional Control: IF• To conditionally execute a statement or sequence of
statements.
Syntax
If <condition> THEN
<sequence of statements>
[ELSIF <condition> THEN
<sequence of statements>]
-- ELSIFs may be repeated
[ELSE
<sequence of statements>]
END IF;!
DECLARE num_jobs NUMBER (7); actor_id actor.actorid%type;BEGIN actor_id := &actor_id; SELECT COUNT(*) INTO num_jobs FROM auditions WHERE actorid = actor_id AND called_back = 'YES'; IF num_jobs > 40 THEN UPDATE actor SET actor_rating = 'OSCAR time' WHERE actorid = actor_id; ELSIF num_jobs > 20 THEN UPDATE actor SET actor_rating = 'daytime soaps' WHERE actorid = actor_id; ELSE UPDATE actor SET actor_rating = 'waiter' where actorid = actor_id; END IF; COMMIT;END;
Conditional Control: IF
!
The NULL trapBLOCK 1: BLOCK 2: If a>=b THEN If b>=a THEN
Do_this…; Do_that…;ELSE ELSE
Do_that…; Do_this ...;END IF ; ENDIF;
– Given any pair of non-NULL values for “a” and “b”,will BLOCK 1 and BLOCK 2 do the same THING?
– What if either “a” or “b” (or both) is NULL?
Conditional Control: IF
!@
Iterative Control• Loops repeat a statement or sequence of statements
multiple times.
Four types of loops:
I. Simple loops
2. Numeric FOR Loops
3. WHILE Loops
4. Cursor FOR loops
!
• Simple Loops repeat a sequence of statements multiple times.
Syntax
LOOP
<sequence of statements>
END LOOP; -- sometimes called
an 'infinite' loop
• Exit Statements exit any type of loop immediately and program
control goes to the immediate statement after the loop
Syntax
EXIT WHEN <condition> ; -- 'infinite' loop insurance
Iterative Control: LOOP and EXIT
!
DECLARE
ctr NUMBER(3) :=0;
BEGIN
LOOPINSERT INTO temp(num,des)
VALUES (ctr,'ITERATION COMPLETE'); ctr := ctr+1;IF ctr = 500 THEN
EXIT;END IF;
END LOOP;
END;
Iterative Control: LOOP and EXIT
!
• Numeric FOR Loops repeat a sequence of statements a fixed number of times.Syntax FOR <index> IN[ REVERSE ]<integer>..<integer> LOOP <sequence of
statements>END LOOP;Quick Notes - Index:
– The Loop Index takes on each value in the range, one at a time, either in forward or reverse order
– It is implicitly of type NUMBER.– It is only defined within the loop.– Value may be referenced in an expression, but a new
value may not be assigned to it within the loop
Iterative Control: FOR
!
Example1 BEGIN
FOR I IN 1..500 LOOPINSERT INTO temp (message) VALUES ('I will not sleep in class.');END LOOP;
END;
Example2DECLARE
my_index CHAR(20) := 'Fettuam'BEGIN
FOR my_index IN REVERSE 21...30 LOOP
/* redeclares my index */INSERT INTO temp (des) VALUES (my_index); /* inserts the numbers 30 through 21 */
END LOOP;END;
Iterative Control: FOR
!@
• WHILE Loops repeat a sequence of statements until a specific condition is no longer TRUE.Syntax
WHILE <condition> LOOP<sequence of statements>
END LOOP;
• Quick Notes:– The term <condition> may be any PL/SQL condition (I.e., it
must return a BOOLEAN value of TRUE, FALSE, or NULL).
– The sequence of statements will be repeated as long as <condition> evaluates to TRUE.
Iterative Control: WHILE
!
DECLARE
ctr NUMBER (3) := 0;
BEGIN
WHILE ctr < 500 LOOP
INSERT INTO temp (message)
VALUES ('Well, might sleep just a little');
ctr := ctr + 1;
END LOOP;
END;
Iterative Control: WHILE
!
CASE STATEMENTCASE selector WHEN expression1 THEN result1 WHEN expression2 THEN result2 ... WHEN expressionN THEN resultN [ELSE resultN+1] END;
CASE WHEN search_condition1 THEN result1 WHEN search_condition2 THEN result2 ... WHEN search_conditionN THEN resultN [ELSE resultN+1] END;
CASE EXAMPLE
• Just another step towards writing cleaner, easier to read and maintain code
DECLARE grade CHAR(1); appraisal VARCHAR2(20);BEGIN ... appraisal := CASE grade WHEN 'A' THEN 'Excellent' WHEN 'B' THEN 'Very Good' WHEN 'C' THEN 'Good' WHEN 'D' THEN 'Fair' WHEN 'F' THEN 'Poor' ELSE 'No such grade' END; ...END;
Case1.sql
• It does nothing other than pass the control to the next statement
Syntax
NULL;
• Quick Notes:
– NULL statement and the Boolean non-value NULL are different
– Make use of NULL in the IF condition for doing nothing in any branch of the condition
Sequential Control: NULL
!
Example1: Minimum PL/SQL block BEGIN
NULL;END;
Example2: Use in IF statementBEGIN
IF <condition> THEN… Statements …
ELSIF <condition> THENNULL; -- do nothing branch of
the IF statementELSE
… Statements …ENDIF;
END;
Sequential Control: NULL
!
• “GO TO” Statements jump to a different place in the PL/SQL block .
Syntax<<label_name>> x:=x + 1; -- a statement label GOTO GOTO label_name; -- jumps to x := x + 1
“GO TO” Statements have 2 parts
• A statement with the label: where you want control to come
back using “GO TO” statement somewhere else in the program
• A statement with “GO TO”: to make control jump to the label.
Sequential Control: GOTO
!
• Quick Notes:
You can only legally GOTO a statement that is either:
1. in the same sequence of statements as the GOTO statement
2 . In the sequence of statements that encloses the GOTO
statement (i.e an outer block)
BEGIN
<<Come_here>> X := X + 1;
... Statements …
GOTO Come_here;-- Now control will jump back
-- to the label Come_here
END;
Sequential Control: GOTO
!
Other Uses for Statement Labels
• Labels may label any statement
• In addition to their use as targets for GOTO statements, labels may be used for:
1.Blocks
2.Loops
• Labelling a block and loop allows referencing of DECLARED objects that would otherwise not be visible because of scope rules.
• Labelling a loop also allows control to exit in outer loops
!@
Other Uses for Statement Labels
Example1:BEGIN
<<sample>> DECLARE
deptno NUMBER :=10; BEGIN DECLARE deptno NUMBER := 20; BEGIN UPDATE emp SET sal = sal * 1.1 WHERE deptno = sample.deptno; COMMIT; END;
END sample;END;
!
Other Uses for Statement Labels
Example2:
«compute_loop»FOR i IN 1..100LOOP
<statements>DECLARE
I NUMBER := 0;BEGIN
INSERT INTO temp (num,des)VALUES (compute_loop.i, 'COMPLETE');
END ;END LOOP compute_loop; -- must include loop name here
!
Other Uses for Statement Labels
Example3:
«outer loop»
WHILE a >b LOOP
b:= b +1;
«inner loop»
WHILE b > c LOOP
C := C + 2;
EXIT outer_loop WHEN c > 200;
END LOOP inner loop;
END LOOP outer_loop;!
User Defined RecordsDECLARE
TYPE DeptRectyp IS
RECORD(deptno number(2),dname char(14),loc char(13));
dept_rec DeptRectyp;
..
BEGIN
SELECT deptno ,dname,loc into dept_rec FROM dept
WHERE deptno = 30;
..
END;
!@
PL/SQL Tables
• Are composed of two components:
– Primary Key of data type BINARY_INTEGER
– Column of scalar or record data type
• Can increase in size dynamically because they are unconstrained
• PL/SQL tables are also called INDEX BY table
!
PL/SQL Tables
• PL/SQL tables declared in two stepsDefine table type
TYPE type_name
IS TABLE OF {column_type | variable%type | table.column%column} [NOT NULL]
INDEX BY BINARY_INTEGER;
Declare PL/SQL table of that type plsql_ table_name type_name;
• To reference rows in a PL/SQL table , specify primary key value using the array like syntax
plsql_table_name(primary_key_value) ename_tab(3)
!
PL/SQL Tables• Assigning values to rows in PL/SQL
tableename (2) := emp.ename
• Neither the primary key nor the column can be named
!
PL/SQL TablesDECLARE
TYPE EnameTabTyp IS TABLE OF emp.ename%TYPE INDEX BY BINARY_INTEGER;
TYPE SalTabTyp IS TABLE OF emp.sal%TYPEINDEX BY BINARY_INTEGER;
ename_tab EnameTabTyp;sal_tab SalTabTyp; I BINARY_INTEGER := 0;...
(Continued on next page)
!
PL/SQL Tables
BEGIN--load employee name and salaries into PL/SQL tables
FOR emprec IN (SELECT ename,sal from emp) LOOPI := I +1;ename_tab(I) := emprec.ename;sal_tab(I) := emprec.sal;
END LOOP;-- process the tablesprocess_sals(ename_tab,sal_tab);
..END;
!
Cursor• A work area to execute SQL statements and store
processing information.• Every SQL DML statement processed by PL/SQL
has an associated CURSOR.• Two Types of CURSORS
– 1. EXPLICIT• Multiple row SELECT Statements
– 2. IMPLICIT• All INSERT Statements• All UPDATE Statements• All DELETE Statements• Single row SELECT....INTO Statements
!@
Explicit Cursor:Use
• STEP 1. Declare the cursorSyntax:
DECLARECURSOR <cursor name>IS <regular select: statement>;
• Quick Notes:– The <regular select statement> must NOT
include the INTO clause in a single-row SELECT...INTO statement
– Declared cursors are scoped just like variables.
!
Explicit Cursor:Use
Example:DECLARE
x NUMBER(7,2); total NUMBER(5);
lower_sal_limit CONSTANT NUMBER(4) := 1200;CURSOR c1 IS SELECT ename FROM empWHERE sal > lower_ sal _limit;
BEGIN…
• STEP 2. Open the cursorSyntax:
OPEN <cursor name>; -- excecutes the query and identifies the result set consisting of all the rows that meet the query criteria.
!@
• STEP 3. Fetch data from the cursorSyntax:
FETCH <cursor name> into <var1, var2..>; -- fetches values to the variable and increments the pointer to the
next value.
• Quick Notes:– Retrieves one row of data from the cursor, and stores it
in the specified variables (similar to how a single-row SELECT works).
– There must be exactly one INTO variable for each column selected by the SELECT statement.
– The first column gets assigned to var1, the second assigned var2, etc.
Explicit Cursor:Use
!@
• STEP 4. Close the cursor
Syntax:CLOSE <cursor name>; -- closes the cursor , and the result set becomes
unidentified
( NOTE: Once a cursor is closed ,it can be reopened . Any other operation on a
closed cursor raises predefined exception INVALID_CURSOR.)
Explicit Cursor: Use
!@
Explicit Cursor:Attributes
• %NOTFOUND LOOP
FETCH my_cursor INTO my_ename, my_sal; EXIT WHEN my_cursor%NOTFOUND; --- process data here
END LOOP;
• %FOUND FETCH my_cursor INTO my_ename, my_ sal;
WHILE my_cursor%FOUND LOOP;
-- process data here
FETCH my_cursor INTO my ename, my_sal;
END LOOP;
!
Explicit Cursor: Attributes• %ROWCOUNT LOOP
FETCH my_cursor INTO my_ename, my_sal; EXIT WHEN (my_cursor%NOTFOUND) OR (my_cursor%ROWCOUNT> 10);
--process data hereEND LOOP;
• %ISOPEN IF my_cursor%ISOPEN THEN
FETCH my_cursor into my_ename,my_sal;
ELSEOPEN my_cursor;
END IF;
!@
Explicit CursorExample: Reopening a cursorDECLARE
total_bonus NUMBER(8,2) := 0;
min _sal emp.sal%TYPE := 1000;
-- start guessing
bonus_ amt emp . sal%TYPE;
CURSOR bonus IS SELECT sal *.10
FROM emp WHERE sal > min_ sal;
(Continued on next page)
!@
Explicit CursorExample: Reopening a cursor
BEGIN -- (Continued from previous page)OPEN bonus; -- uses min_ sal value of 1000LOOP
FETCH bonus INTO bonus_amt; EXIT WHEN bonus%NOTFOUND;
total_bonus := total_bonus + bonus_amt; IF total_bonus > 2000 THEN
/* up the minimum and try again */ min_sal :=min_sal + 500;
total_bonus := 0; -- reset the total
OPEN bonus; -- re-open with new min _sal
END IF;END LOOP; --you may want to store min_sal somewhere
CLOSE bonus;END;
!@
Explicit Cursor: FOR loops• Cursor FOR Loops specify a sequence of statements to be repeated once for each row that is returned by the cursor.Syntax
FOR <record_name> IN <cursor_name> LOOP-- statements to be repeated
go hereEND LOOP;
• Numeric FOR Loop Similarities– Specify a Set of rows from a table by using the cursor's
name v/s. Specifying a set of integers (i.e. 1..10)– Index takes on the values of each row v/s index taking on
integer values (i.e. 1 through 10).
!
Explicit Cursor: FOR loopsConceptual Cursor Loop Model
LOOPS:– When a cursor loop is initiated, an implicit OPEN
cursor_name is executed.
– For each row that satisfies the query associated with the cursor, an implicit FETCH is executed into the components of record_name.
– when there are no more rows left to FETCH, an implicit CLOSE cursor_name is executed and the loop is exited.
!
Explicit Cursor: FOR loopsDECLAREsal_limit NUMBER(4) := 0;total_sal NUMBER(9,2):=0;CURSOR my_cursor IS SELECT ename,sal FROM emp WHERE sal > sal_limit;
BEGINsal_limit := 1200;FOR cursor_row IN my_cursor LOOP
INSERT INTO temp(message,num) VALUES (cursor_row.ename, cursor_row.sal);
total_sal := total_sal + cursor_row.sal;END LOOP;
COMMIT;END;
!@
Implicit Cursor• An Implicit Cursor is automatically associated with any SQL DML statement that does not have an explicit cursor associated with it.– INSERT, UPDATE , DELETE, SELECT...INTO
• Quick Notes:– Implicit cursor is called the "SQL'' cursor - it stores
information concerning the processing of the last SQL statement not associated with an explicit cursor
– OPEN, FETCH, and CLOSE don't apply.
– All cursor attributes apply.
!@
Implicit Cursor: Attributes• SQL %NOTFOUND UPDATE emp SET sal = sal*10.0 WHERE ename = 'WARD';IF SQL%NOTFOUND THEN -- WARD wasn't found
INSERT INTO emp(empno, ename, sal) VALUES (4, 'WARD', 9999);
END IF;
• SQL %FOUND
• SQL%ROWCOUNT DELETE FROM baseball_team WHERE batting_avg< . 100;IF SQL%ROWCOUNT > 5 THEN
INSERT INTO temp (message)VALUES ('Your team needs help.')
END IF;
• SQL%ISOPEN (always evaluates to FALSE)
!@
BREAK
