foreign key in sql
Foreign Key:
It is a column that comes from a different table and
using Foreign key tables are related each other
It is the primary key of another table
It can be duplicate or null for another table
Primary Key :
It is unique column in every table in a database
It can ONLY accept;
- nonduplicate values
- cannot be NULL
Unique Key:
Only unique value and also can contain NULLhow to set foreign key in sql server
CREATE TABLE Orders (
OrderID int NOT NULL,
OrderNumber int NOT NULL,
PersonID int,
PRIMARY KEY (OrderID),
FOREIGN KEY (PersonID) REFERENCES Persons(PersonID)
);Copyright © 2021 Codeinu
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