Drop a Foreign Key

ALTER TABLE statement is used to drop a foreign key from a table once it has been created.

Syntax:

ALTER TABLE table_name  

DROP CONSTRAINT fk_name;

Parameter explanation

table_name: It specifies the name of the table where the foreign key has been created.

fk_name: It specifies the name of the foreign key that you want to remove.

Example:

In the previous example we have seen how to create a foreign key.

CREATE TABLE products  
( product_id INT PRIMARY KEY,  
  product_name VARCHAR(50) NOT NULL,  
  category VARCHAR(25)  
);  
CREATE TABLE inventory  
( inventory_id INT PRIMARY KEY,  
  product_id INT NOT NULL,  
  quantity INT,  
  min_level INT,  
  max_level INT,  
  CONSTRAINT fk_inv_product_id  
    FOREIGN KEY (product_id)  
    REFERENCES products (product_id)  
);  

Use the following command to drop the foreign key called fk_inv_product_id.

ALTER TABLE [javatpoint].[dbo].[inventory]  

DROP CONSTRAINT fk_inv_product_id;

Output:

Now the foreign key is dropped.