CASCADE in SQL Server with Example

Use the ON DELETE CASCADE option if you want rows deleted in the child table when corresponding rows are deleted in the parent table. If you do not specify cascading deletes, the default behavior of the database server prevents you from deleting data in a table if other tables reference it.

If you specify this option, when you delete a row in the parent table, the database server also deletes any rows associated with that row (foreign keys) in a child table. The advantage of the ON DELETE CASCADE option is that it allows you to reduce the quantity of SQL statements needed to perform delete actions.

select * from dbo.ProductDetails
select * from dbo.Products

CREATE TABLE [dbo].[Products](
[ProductID] [int] NOT NULL,
[ProductDesc] [varchar](50) NOT NULL,
CONSTRAINT [PK_Products] PRIMARY KEY CLUSTERED
(
[ProductID] ASC
)) ON [PRIMARY]

CREATE TABLE [dbo].[ProductDetails](
[ProductDetailID] [int] NOT NULL,
[ProductID] [int] NOT NULL,
[Total] [int] NOT NULL,
CONSTRAINT [PK_ProductDetails] PRIMARY KEY CLUSTERED
(
[ProductDetailID] ASC
)) ON [PRIMARY]
GO

ALTER TABLE [dbo].[ProductDetails] WITH CHECK ADD CONSTRAINT 
[FK_ProductDetails_Products] FOREIGN KEY([ProductID])
REFERENCES [dbo].[Products] ([ProductID])
ON UPDATE CASCADE
ON DELETE CASCADE

INSERT INTO Products (ProductID, ProductDesc)
SELECT 1, 'Bike'
UNION ALL
SELECT 2, 'Car'
UNION ALL
SELECT 3, 'Books'

INSERT INTO ProductDetails
([ProductDetailID],[ProductID],[Total])
SELECT 1, 1, 200
UNION ALL
SELECT 2, 1, 100
UNION ALL
SELECT 3, 1, 111
UNION ALL
SELECT 4, 2, 200
UNION ALL
SELECT 5, 3, 100
UNION ALL
SELECT 6, 3, 100
UNION ALL
SELECT 7, 3, 200

SELECT *
FROM Products
SELECT *
FROM ProductDetails

DELETE
FROM Products
WHERE ProductID = 1

DROP TABLE ProductDetails
DROP TABLE Products