SQL Constraints(FOREIGN KEY)

A FOREIGN KEY as a relationships in one table points to a PRIMARY KEY in another table.

we will create a CREATE TABLE script for these tables:


DtlPermission:

CREATE TABLE DtlPermission
(
Member_Id int NULL,
  GroupId int NULL,
  Can_View_Sale_Lead bit NULL,
  Can_View_Buy_Lead bit NULL,
  Can_Sale bit NULL,
  Can_Buy bit NULL,
  Up_To_Date date NULL
 ) ON [PRIMARY]

MstGroup:

CREATE TABLE MstGroup
 (
      GroupId int NOT NULL FOREIGN KEY REFERENCES DtlPermission(GroupId),                       Groupname nvarchar(100) NULL
 ) 

The FOREIGN KEY constraint prevents that invalid data from being inserted into the foreign key column.