foreign key constraint in ms sql
/*Creating Foreign Key Constraint*/
ALTER TABLE ForeignKeyTable ADD CONSTRAINT ForeignKeyTable_foreignKeyColumn_FK
FOREIGN KEY (foreignKeyColumn) REFERENCES PrimaryKeyTable (PrimaryKeyColumn)foreign key constraint in ms sql
/*Creating Foreign Key Constraint*/
ALTER TABLE ForeignKeyTable ADD CONSTRAINT ForeignKeyTable_foreignKeyColumn_FK
FOREIGN KEY (foreignKeyColumn) REFERENCES PrimaryKeyTable (PrimaryKeyColumn)foreign key in sql
A FOREIGN KEY is a key used to link two tables together.
A FOREIGN KEY is a field (or collection of fields) in one table that refers to the PRIMARY KEY in another table.
The table containing the foreign key is called the child table, and the table containing the candidate key is called the referenced or parent table.
Example:
# creating table users
CREATE TABLE users(
user_id INT NOT NULL,
user_name VARCHAR(64) NOT NULL,
user_pass VARCHAR(32) NOT NULL,
PRIMARY KEY(user_id);
);
# adding user data
INSERT INTO users VALUES(1,"Raj","raj@123");
# creating table orders
CREATE TABLE orders(
order_id INT NOT NULL,
order_description VARCHAR(255),
orderer_id INT NOT NULL,
PRIMARY KEY(order_id),
FOREIGN KEY (orderer_id) REFERENCES users(user_id)
);
# adding order data
INSERT INTO orders VALUES(1,"Daily groceries",1);sql server foreign key
CREATE TABLE Orders (
OrderID int NOT NULL PRIMARY KEY,
OrderNumber int NOT NULL,
PersonID int FOREIGN KEY REFERENCES Persons(PersonID)
);Copyright © 2021 Codeinu
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