DatabaseManagementSystems/Practical/Practical Exam/PL-SQL/P10 - Trigger.md

P10 - Trigger

Problem Statement: Trigger: Write a after trigger for Insert, update and delete event considering following requirement: Emp(Emp_no, Emp_name, Emp_salary) a) Trigger should be initiated when salary tried to be inserted is less than Rs.50,000/- b) Trigger should be initiated when salary tried to be updated for value less than Rs. 50,000/- Also the new values expected to be inserted will be stored in new table Tracking(Emp_no,Emp_salary).

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Creating tables:

CREATE TABLE Emp(
    Emp_no NUMBER(14),
    Emp_name VARCHAR(255),
    Emp_salary NUMBER(14)
);

CREATE TABLE Tracking(
    Emp_no NUMBER(14),
    Emp_salary NUMBER(14)
);

Trigger

CREATE OR REPLACE TRIGGER P10
AFTER INSERT OR UPDATE ON Emp
FOR EACH ROW
BEGIN
	IF inserting THEN
		IF (:New.Emp_salary < 50000) THEN
			insert into Tracking (Emp_no, Emp_salary) VALUES (:New.Emp_no, :New.Emp_salary);
			DBMS_OUTPUT.PUT_LINE('Inserting record with salary < 50000');
		END IF;
	ELSIF updating THEN
		IF (:New.Emp_salary < 50000) THEN
			UPDATE Tracking SET Emp_salary = :New.Emp_salary WHERE Emp_no = :Old.Emp_no;
			DBMS_OUTPUT.PUT_LINE('Updated value of salary < 50000 for a record');
		END IF;
	END IF;
END;
/

1. After performing insertion operation:

INSERT INTO Emp VALUES (1, 'Tanmay', 45000);
INSERT INTO Emp VALUES (2, 'Rajesh', 35000);

Output

1 row(s) inserted.
Inserting record with salary < 50000

1 row(s) inserted.
Inserting record with salary < 50000

Tracking:
EMP_NO EMP_SALARY
1 45000
2 35000

2. After performing update operation:

UPDATE Emp SET Emp_salary = 43000 WHERE Emp_no = 1;

Output

1 row(s) updated.
Updated value of salary < 50000 for a record

Tracking:
EMP_NO EMP_SALARY
1 43000
2 35000

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