SQL Constraints- Foreign key

nDefining a foreign key establishes a referential constraint between the foreign key (Child table) and the primary key (parent table)

Create-Foreign key

CREATE TABLE EMPtbl2( (EMPID int NOT NULL, EMPname varchar(255) NOT NULL,company varchar(255),salary varchar(255),City varchar(255),    primary key (salary) constraint fk_EMPtbl2 FOREIGN KEY(EMPID1) REFERENCES EMPtbl1(EMPID)

Alter-Foreign key

ALTER TABLE EMPtbl2

ADD CONSTRAINT fk_EMPtbl2 FOREIGN KEY (EMPID, salary)

Drop-Foreign key

ALTER TABLE EMPtbl2

DROP CONSTRAINT fk_EMPtbl2