ON UPDATE OF EMPLOYEE.salary
  IF NEW.salary > 100000 THEN
    EXECUTE IncreaseJobLevel(NEW.enumber, NEW.salary);
  END IF;

	     
ON UPDATE OF EMPLOYEE.salary
  IF EXTRACT(CURRENT_DATE,'Day')) IN ('Saturday', 'Sunday') THEN
    RAISE EXCEPTION 'Salary cannot be updated over a weekend !';
  END IF;

ON UPDATE OF EMPLOYEE.salary

IF NEW.salary > 100000

EXECUTE IncreaseJobLevel(NEW.enumber, NEW.salary);

CREATE OR REPLACE TRIGGER CheckBudget

  
BEFORE

  
UPDATE OF budget ON DEPARTMENT

 
FOR EACH ROW                  -- FOR EACH ROW means that it is a row trigger

EXECUTE PROCEDURE CheckBudget();

CREATE OR REPLACE FUNCTION CheckBudget()
RETURNS TRIGGER AS
$$
BEGIN

 
  IF NOT ( NEW.budget BETWEEN 1 AND 7000 ) THEN

 
    RAISE EXCEPTION 'Budget of department % cannot be equal to %',
	            NEW.name, NEW.budget;
  END IF;

  RETURN NEW;

END;
$$
LANGUAGE plpgsql;

CREATE OR REPLACE TRIGGER CheckBudget
  BEFORE UPDATE OF budget ON DEPARTMENT
  FOR EACH ROW                
    EXECUTE PROCEDURE CheckBudget();

CREATE OR REPLACE FUNCTION CheckBudget()
RETURNS TRIGGER AS
$$
BEGIN
  IF NOT ( NEW.budget BETWEEN 1 AND 7000 ) THEN
    RAISE EXCEPTION 'Budget of department % cannot be equal to %',
	            NEW.name, NEW.budget;
  END IF;
  RETURN NEW;
END;
$$
LANGUAGE plpgsql;

CREATE OR REPLACE TRIGGER CheckBudget
  BEFORE UPDATE OF budget ON DEPARTMENT
  FOR EACH ROW
    WHEN ( NOT ( NEW.budget BETWEEN 1 AND 7000 ) )            
      EXECUTE PROCEDURE AbortUpdate();

CREATE OR REPLACE FUNCTION AbortUpdate()
RETURNS TRIGGER AS
$$
BEGIN
  RAISE EXCEPTION 'Budget of department % cannot be equal to %', 
                   NEW.name, NEW.budget;
  RETURN NEW;
END;
$$
LANGUAGE plpgsql;

 
UPDATE DEPARTMENT
SET budget = 100000
WHERE name = 'Physics';
ERROR:  Budget of department Physics cannot be equal to 100000.0
CONTEXT:  PL/pgSQL function abortupdate() line 3 at RAISE;

 
UPDATE DEPARTMENT
SET budget = 100
WHERE name = 'Physics';
UPDATE 1

 
BEFORE UPDATE ON DEPARTMENT

 
AFTER DELETE ON COURSE

 
INSTEAD OF INSERT ON EMPVIEW

 
AFTER INSERT OR DELETE ON DEPARTMENT

 
BEFORE UPDATE OF budget ON DEPARTMENT

 
BEFORE UPDATE OF cnum, title ON COURSE

 
AFTER INSERT ON DEPARTMENT

 
INSTEAD OF TRUNCATE ON DEPARTMENT

 
AFTER DELETE OR INSERT OR UPDATE ON COURSE

WHEN (NEW.budget > 7000)

WHEN (OLD.budget < 1000 AND NEW.budget > 2000);

WHEN (NEW.amount > 1000 );

WHEN (OLD.credits IN (6, 12));

  
CREATE OR REPLACE TRIGGER Audit

  
  AFTER DELETE OR INSERT ON DEPARTMENT

  FOR EACH STATEMENT
    EXECUTE FUNCTION InsertAudit();

CREATE TABLE AUDIT (
  statement VARCHAR(10) NOT NULL,
  date_time TIMESTAMP   NOT NULL,
    CONSTRAINT AUDIT_PK PRIMARY KEY (date_time) );

  
CREATE OR REPLACE FUNCTION InsertAudit()
RETURNS TRIGGER AS
$$
BEGIN
  INSERT INTO AUDIT VALUES(TG_OP, current_timestamp);
  RETURN NULL;
END;
$$
LANGUAGE plpgsql;

  
INSERT INTO DEPARTMENT VALUES ('Quantum Computers','QC',30,'Kate',223426.9 );
DELETE FROM DEPARTMENT WHERE name = 'Arts';
DELETE FROM DEPARTMENT;

  
SELECT * FROM AUDIT;
 statement |         date_time          
-----------+----------------------------
 INSERT    | 2023-12-06 14:08:20.475765
 DELETE    | 2023-12-06 14:08:33.19901
 DELETE    | 2023-12-06 14:08:41.729328

BEFORE INSERT ON DEPARTMENT

AFTER UPDATE ON EMPLOYEE

 
AFTER DELETE ON PROJECT

CREATE OR REPLACE TRIGGER UpdateDepartment

  AFTER UPDATE ON DEPARTMENT

  FOR EACH ROW
    EXECUTE FUNCTION UpdateDepartment();

 
CREATE TABLE AUDIT (
  statement VARCHAR(10)  NOT NULL,
  date_time TIMESTAMP    NOT NULL,
  name      VARCHAR(50)  NOT NULL,
  oldbudget DECIMAL(9,1) NOT NULL,
  newbudget DECIMAL(9,1) NOT NULL);

     
CREATE OR REPLACE FUNCTION UpdateDepartment()
RETURNS TRIGGER AS
$$
BEGIN
  INSERT INTO AUDIT VALUES(TG_OP, current_timestamp, OLD.name, OLD.budget,
                                                               NEW.budget);
  RETURN NULL;
END;
$$
LANGUAGE plpgsql;

     
UPDATE DEPARTMENT SET budget = budget + 1000;
UPDATE 7

  
SELECT * FROM AUDIT;
statement |         date_time          |       name        | oldbudget | newbudget
----------+----------------------------+-------------------+-----------+-----------
 UPDATE   | 2023-12-06 18:56:03.402062 | Computer Science  |  223426.9 |  224426.9
 UPDATE   | 2023-12-06 18:56:03.402062 | Physics           |  223453.9 |  224453.9
 UPDATE   | 2023-12-06 18:56:03.402062 | Engineering       |  313455.9 |  314455.9
 UPDATE   | 2023-12-06 18:56:03.402062 | Mathematics       |  133456.9 |  134456.9
 UPDATE   | 2023-12-06 18:56:03.402062 | Education         |  173557.9 |  174557.9
 UPDATE   | 2023-12-06 18:56:03.402062 | Science           |  163459.9 |  164459.9
 UPDATE   | 2023-12-06 18:56:03.402062 | Quantum Computers |  223426.9 |  224426.9
(7 rows)