Compound Triggers v13

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The following example of a compound trigger records a change to the employee salary by defining a compound trigger (named hr_trigger) on the emp table.

First, create a table named emp.

CREATE TABLE emp(EMPNO INT, ENAME TEXT, SAL INT, DEPTNO INT);
CREATE TABLE

Then, create a compound trigger named hr_trigger. The trigger utilizes each of the four timing-points to modify the salary with an INSERT, UPDATE, or DELETE statement. In the global declaration section, the initial salary is declared as 10,000.

CREATE OR REPLACE TRIGGER hr_trigger
  FOR INSERT OR UPDATE OR DELETE ON emp
    COMPOUND TRIGGER
  -- Global declaration.
  var_sal NUMBER := 10000;

  BEFORE STATEMENT IS
  BEGIN
    var_sal := var_sal + 1000;
    DBMS_OUTPUT.PUT_LINE('Before Statement: ' || var_sal);
  END BEFORE STATEMENT;

  BEFORE EACH ROW IS
  BEGIN
    var_sal := var_sal + 1000;
    DBMS_OUTPUT.PUT_LINE('Before Each Row: ' || var_sal);
  END BEFORE EACH ROW;

  AFTER EACH ROW IS
  BEGIN
    var_sal := var_sal + 1000;
    DBMS_OUTPUT.PUT_LINE('After Each Row: ' || var_sal);
  END AFTER EACH ROW;

  AFTER STATEMENT IS
  BEGIN
    var_sal := var_sal + 1000;
    DBMS_OUTPUT.PUT_LINE('After Statement: ' || var_sal);
  END AFTER STATEMENT;

END hr_trigger;

Output: Trigger created.

INSERT the record into table emp.

INSERT INTO emp (EMPNO, ENAME, SAL, DEPTNO) VALUES(1111,'SMITH', 10000, 20);

The INSERT statement produces the following output:

Before Statement: 11000
Before each row: 12000
After each row: 13000
After statement: 14000
INSERT 0 1

The UPDATE statement will update the employee salary record, setting the salary to 15000 for a specific employee number.

UPDATE emp SET SAL = 15000 where EMPNO = 1111;

The UPDATE statement produces the following output:

Before Statement: 11000
Before each row: 12000
After each row: 13000
After statement: 14000
UPDATE 1

SELECT * FROM emp;
 EMPNO | ENAME |  SAL  | DEPTNO
-------+-------+-------+--------
  1111 | SMITH | 15000 |     20
(1 row)

The DELETE statement deletes the employee salary record.

DELETE from emp where EMPNO = 1111;

The DELETE statement produces the following output:

Before Statement: 11000
Before each row: 12000
After each row: 13000
After statement: 14000
DELETE 1

SELECT * FROM emp;
 EMPNO | ENAME | SAL | DEPTNO
-------+-------+-----+--------
(0 rows)

The TRUNCATE statement removes all the records from the emp table.

CREATE OR REPLACE TRIGGER hr_trigger
  FOR TRUNCATE ON emp
    COMPOUND TRIGGER
  -- Global declaration.
  var_sal NUMBER := 10000;
  BEFORE STATEMENT IS
  BEGIN
    var_sal := var_sal + 1000;
    DBMS_OUTPUT.PUT_LINE('Before Statement: ' || var_sal);
  END BEFORE STATEMENT;

  AFTER STATEMENT IS
  BEGIN
    var_sal := var_sal + 1000;
    DBMS_OUTPUT.PUT_LINE('After Statement: ' || var_sal);
  END AFTER STATEMENT;

END hr_trigger;

Output: Trigger created.

The TRUNCATE statement produces the following output:

TRUNCATE emp;
Before Statement: 11000
After statement: 12000
TRUNCATE TABLE
Note

The TRUNCATE statement may be used only at a BEFORE STATEMENT or AFTER STATEMENT timing-point.

The following example creates a compound trigger named hr_trigger on the emp table with a WHEN condition that checks and prints employee salary whenever a INSERT, UPDATE, or DELETE statement affects the emp table. The database evaluates the WHEN condition for a row-level trigger, and the trigger is executed once per row if the WHEN condition evaluates to TRUE. The statement-level trigger is executed irrespective of the WHEN condition.

CREATE OR REPLACE TRIGGER hr_trigger
  FOR INSERT OR UPDATE OR DELETE ON emp
  REFERENCING NEW AS new OLD AS old
  WHEN (old.sal > 5000 OR new.sal < 8000)
    COMPOUND TRIGGER

  BEFORE STATEMENT IS
  BEGIN
    DBMS_OUTPUT.PUT_LINE('Before Statement');
  END BEFORE STATEMENT;

  BEFORE EACH ROW IS
  BEGIN
    DBMS_OUTPUT.PUT_LINE('Before Each Row: ' || :OLD.sal ||' ' || :NEW.sal);
  END BEFORE EACH ROW;

  AFTER EACH ROW IS
  BEGIN
    DBMS_OUTPUT.PUT_LINE('After Each Row: ' || :OLD.sal ||' ' || :NEW.sal);
  END AFTER EACH ROW;

  AFTER STATEMENT IS
  BEGIN
    DBMS_OUTPUT.PUT_LINE('After Statement');
  END AFTER STATEMENT;

END hr_trigger;

Insert the record into table emp.

INSERT INTO emp(EMPNO, ENAME, SAL, DEPTNO) VALUES(1111, 'SMITH', 1600, 20);

The INSERT statement produces the following output:

Before Statement
Before Each Row: 1600
After Each Row: 1600
After Statement
INSERT 0 1

The UPDATE statement will update the employee salary record, setting the salary to 7500.

UPDATE emp SET SAL = 7500 where EMPNO = 1111;

The UPDATE statement produces the following output:

Before Statement
Before Each Row: 1600 7500
After Each Row: 1600 7500
After Statement
UPDATE 1

SELECT * from emp;
 empno | ename | sal  | deptno
-------+-------+------+--------
  1111 | SMITH | 7500 |     20
(1 row)

The DELETE statement deletes the employee salary record.

DELETE from emp where EMPNO = 1111;

The DELETE statement produces the following output:

Before Statement
Before Each Row: 7500
After Each Row: 7500
After Statement
DELETE 1

SELECT * from emp;
 empno | ename | sal | deptno
-------+-------+-----+--------
(0 rows)
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