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FOREIGN KEY WITH DELETE CASCADE

DELETE CASCADE: Foreign key delete cascade means when parent table records is deleted the corresponding child table records also deleted.
--CREATE DEMOS DATABASE
CREATE DATABASE DEMOS
USE DEMOS

CREATE TABLE DBO.DEPT
(
            ID INT PRIMARY KEY,
            DEPTNAME VARCHAR(100)
)


--INSERT DATA TO DEPT TABLE
INSERT INTO DBO.DEPT(ID,DEPTNAME) VALUES(1,'SOFTWARE'),(2,'BPO')


--CREATE EMP TABLE
CREATE TABLE DBO.EMP
(
            ID INT IDENTITY(1,1) PRIMARY KEY,
            FIRTSNAME VARCHAR(100) ,
            LASTNAME VARCHAR(100),
            LOCATION VARCHAR(100),
            DOB DATETIME,
            SALARY MONEY,
            DEPT INT
)

--ADD FOREIGN KEY TO EMP TABLE
ALTER TABLE DBO.EMP
ADD CONSTRAINT FK_DEPTID FOREIGN KEY (DEPT)
REFERENCES DBO.DEPT(ID) ON DELETE CASCADE ON UPDATE CASCADE

--INSERT SOME DATA TO EMP TABLE
INSERT INTO DBO.EMP(FIRTSNAME,LASTNAME,LOCATION,DOB,SALARY,DEPT)
VALUES
('RAKESH','KALLURI','HYDERABAD','07-23-1989',24000,1),
('NARESH','CH','PUNE','07-23-1987',48000,1),
('SRUJAN','KUMAR','HYDERABAD','07-23-1988',25000,1),
('VENKATESH','BODUPPALY','HYDERABAD','07-23-1986',32000,2),
('ALI','MD','HYDERABAD','07-23-1987',38000,2),
('GANGA','RAJAYAM','PUNE','05-26-1987',390000,2),
('RAVI','KUMAR','CHENNAI','03-23-1986',47000,1),
('PRAVEEN','KUMAR','DELHI','07-23-1988',33000,2)


SELECT * FROM DBO.DEPT













SELECT * FROM DBO.EMP











DELETE FROM  DBO.DEPT WHERE ID=1

Whenever we are trying to Delete records from DEPT table Whose DEPTID Is 1, this child EMP table records also get deleted.













--CHECK THE RECORDS AFTER DELETE
 SELECT * FROM DBO.EMP



                       


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