Cursor: cursor is a private sql work area. Every sql statement executed by oracle server has an individual cursor associated with it.
Cursor are two types
1.Implicit cursor
2.Explicit cursor
Cursor are two types
1.Implicit cursor
2.Explicit cursor
Implicit cursor: Implicit cursors are declared by pl/sql implicitly at the time of DML statement and select statement in pl/sql including queries that returns single row.
Cursor have four attributes
1. SQL%ROWCOUNT
2. SQL%ISOPEN
3. SQL%NOTFOUND
4. SQL%FOUND
1. SQL%ROWCOUNT
2. SQL%ISOPEN
3. SQL%NOTFOUND
4. SQL%FOUND
SQL%ROWCOUNT-Basically it returns number. means number of rows affected by present sql statement.
SQL%ISOPEN-Always evalutes false because implicit cursor automatically closed after execution of sql statement.
SQL%FOUND-Always evalutes true because one or more rows are affected by recent sql statement
SQL%NOTFOUND-Always evalutes true when no rows are affected by present sql statement.
SQL%ISOPEN-Always evalutes false because implicit cursor automatically closed after execution of sql statement.
SQL%FOUND-Always evalutes true because one or more rows are affected by recent sql statement
SQL%NOTFOUND-Always evalutes true when no rows are affected by present sql statement.
Explicit Cursor:
Example of explicit cursor
DECLARE
v_empno employees.employee_id%TYPE;
v_name employees.last_name%TYPE;
CURSOR emp_cur IS
SELECT employee_id,last_name FROM employees
BEGIN
OPEN emp_cur;
LOOP
FETCH emp_cur INTO v_empno,v_name ;
EXIT WHEN emp_cur%ROWCOUNT>10 OR
emp_cur%NOTFOUND;
DBMS_OUTPUT.PUT_LINE('employee_id:'||TO_CHAR(v_empno) || 'employee_name:'||'v_name');
END LOOP;
CLOSE emp_cur;
END;
Trigger Trigger is pl/sql block or procedure that is associated with table,view,schema and database. Execute immediately when particular event take place.
There are two types of trigger
1.Application trigger: Fires automatically when event occurs with particular application.
2.Database trigger: Fires when data such as DML oparation occured at that time.
DML triggers are two types
1.Statementlevel trigger
2.Rowlevel trigger
Statement level trigger -Statement level trigger means trigger body execute once for the triggering event.this is default.A statement level trigger fire once even no rows are affected at all.
Row level- Trigger body execute once for each row affected by triggering event.if no rows are affected in that case trigger body not executed.
CREATE OR REPLACE TRIGGER secure_emp
BEFORE INSERT ON employees
BEGIN
TO_CHAR(SYSDATE,'DY')IN('SUN','SAT') OR TO_CHAR((SYSDATE,'HH24:MI')NOT BETWEEN '08:00' AND '18:00')THEN
RAISE_APPLICATION_ERROR(-20253,'u may insert employee information at business hrs');
END;
