PL/SQL Cursors

PL/SQL Cursors

Cursors n

Cursors allow embedded SQL statements n Result is a set (table) in a temporary work area

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Cursor name permits iterative manipulation of rows

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Two varieties of cursors n Implicit n Explicit More detailed to write, Permit more advanced manipulations

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Example A SIMPLE CURSOR

A SIMPLE CURSOR Declare cursor c1 is select * from emp; BEGIN for emp_rec in c1 loop dbms_output.put_line(emp_rec.ename); end loop; END;

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SQL> create or replace procedure sumsalary IS cursor c1 is select * from emp;

Declaration

salsum integer; BEGIN salsum := 0; for emp_rec in c1 loop salsum := salsum + emp_rec.sal; end loop; dbms_output.put_line('Salary sum: ' || salsum); END; Procedure created.

SQL> execute sumsalary; Salary sum: 29025 PL/SQL procedure successfully completed.

Explicit Cursor Operations n

DECLARE n Introduces cursor object, bound to SQL statement

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OPEN n Constructs temporary table

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FETCH n Accesses next row

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TESTS n %FOUND, %NOTFOUND, %ROWCOUNT, %ISOPEN

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CLOSE n Releases temporary table and associated working data

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DECLARE

Introduces cursor object, bound to SQL statement CURSOR EMP_CUR IS select empno, ename, sal from emp;

OPEN

Constructs temporary table BEGIN open emp_cur;

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FETCH accesses next row LOOP fetch emp_cur into v_empno, v_ename, v_sal;

TESTS %FOUND, %NOTFOUND, %ROWCOUNT, %ISOPEN LOOP fetch emp_cur into v_empno, v_ename, v_sal; EXIT when emp_cur%NOTFOUND; IF (v_sal > 1000) then DBMS_OUTPUT.put_line(v_empno || ' ' || v_ename || ' ' || v_sal);

ELSE DBMS_OUTPUT.put_line(v_ename || ' sal is less then 1000'); END IF; END LOOP;

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CLOSE Releases temporary table and associated working data close emp_cur;

Writing complete Explicit Cursor A complete example Just Remember

DECLARE

OPEN

FETCH

TESTS

CLOSE

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Example Problem We will retrieve all records from EMP table and display them one by one by using CURSOR. With some data manipulation.

CREATE OR REPLACE PROCEDURE MY_TEST IS v_empno emp.empno%type; v_ename emp.ename%type; DECLARE v_sal emp.sal%type; CURSOR EMP_CUR IS select empno, ename, sal from emp; BEGIN open emp_cur; OPEN LOOP fetch emp_cur into v_empno, v_ename, v_sal; FETCH EXIT when emp_cur%NOTFOUND; TESTS IF (v_sal > 1000) then DBMS_OUTPUT.put_line(v_empno || ' ' || v_ename || ' ' || v_sal); ELSE DBMS_OUTPUT.put_line(v_ename || ' sal is less then 1000'); END IF; END LOOP; close emp_cur; CLOSE DBMS_OUTPUT.put_line('Execution Complete'); END;

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Example-2

DECLARE a emp.empno%TYPE; b emp.ename%TYPE; CURSOR T1Cursor IS

/* Cursor declaration: */

SELECT empno, ename FROM emp; BEGIN OPEN T1Cursor; LOOP /* Retrieve each row of the result of the above query into variables: */ FETCH T1Cursor INTO a, b; /* If there are no more rows to fetch, exit the loop: */ EXIT WHEN T1Cursor%NOTFOUND; DBMS_output.put_line(a || ' , ' || b); END LOOP; /* Free cursor used by the query. */ CLOSE T1Cursor; END;

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Example-3 Using %ROWTYPE

Declare CURSOR EMP_CUR IS Defining ROWTYPE variable select * from emp; var_cur EMP%ROWTYPE; BEGIN open emp_cur; FETCH LOOP fetch emp_cur into var_cur; EXIT when emp_cur%NOTFOUND; DBMS_OUTPUT.PUT_LINE(var_cur.empno || ' ' || var_cur.ename ||' ' || var_cur.job || ' ' ||var_cur.mgr || ' ' || var_cur.hiredate|| ' ' ||var_cur.sal || ' ' || var_cur.deptno);

END LOOP; close emp_cur; DBMS_OUTPUT.put_line('Execution Complete');

END; /

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Example 4 Fetching Limited rows

Declare CURSOR EMP_CUR IS ws o r select * from emp; ited m var_cur EMP%ROWTYPE; i l ng i BEGIN h c Fet open emp_cur; LOOP fetch emp_cur into var_cur; EXIT when emp_cur%ROWCOUNT = 5; DBMS_OUTPUT.PUT_LINE(var_cur.empno || ' ' || var_cur.ename ||' ' || var_cur.job || ' ' ||var_cur.mgr || ' ' || var_cur.hiredate|| ' ' ||var_cur.sal || ' ' || var_cur.deptno);

END LOOP; close emp_cur; DBMS_OUTPUT.put_line('Execution Complete');

END; /

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Practice

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Write a cursor that will display last five row from emp table and also all rows that contain salary between 1000 to 2000.

Creating Functions

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Function Syntax CREATE [OR REPLACE] FUNCTION (argument 1 argument 2

[MODE 1] [MODE 2]

datatype-1, datatype-2)

RETURN Number IS PLSQL BLOCK;

A Simple Function CREATE OR REPLACE FUNCTION TEST (v_id in number) return number IS a number; BEGIN a := v_id +100; return a; end test;

Execute a function Here :Z is a SQL variable SQL> variable z number; SQL> execute :z := test(10); PL/SQL procedure successfully completed.

SQL> print z; Z --------110

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Creating Function 2nd Example

CREATE OR REPLACE FUNCTION GET_SAL (v_id in emp.empno%type) return number IS v_salary emp.sal%type := 0 ; BEGIN select sal into v_salary from emp where empno = v_id; return (v_salary); end get_sal; SQL> variable a number; SQL> Execute :a := get_sal(7934); SQL> Print a;

SQL> print a; A --------1300

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Thanks Next:- PLSQL Packages

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