Question

Wondering if you could help me with a simple SQL query.

I have included a simple script to create the 2 tables and 01 SP. With some very small data. Any suggestions? Thanks

I have 2 tables

• Customer
• CustomerItem

The SQL query should:

1. Delete all the items from CustomerItem table based on CustomerStoreID.
2. Delete the customer as well BUT only when the customer has no children anymore

Script to create tables and some data:

BEGIN TRANSACTION;

IF EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'[dbo].[Customer]') AND type in (N'U'))
   DROP TABLE [dbo].[Customer]
GO

SET ANSI_NULLS ON
SET QUOTED_IDENTIFIER ON
GO

CREATE TABLE [dbo].[Customer]
   ([CustomerID] [int] NOT NULL,
    [Name] [nvarchar](50) NOT NULL,
    [Surname] [nvarchar](50) NOT NULL,

    CONSTRAINT [PK_Customer] 
    PRIMARY KEY CLUSTERED ([CustomerID] ASC)
   ) ON [PRIMARY]

IF  EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'[dbo].[CustomerItem]') AND type in (N'U'))
   DROP TABLE [dbo].[CustomerItem]
GO

SET ANSI_NULLS ON
SET QUOTED_IDENTIFIER ON
GO

CREATE TABLE [dbo].[CustomerItem]
   ([CustomerItemID] [int] NOT NULL,
    [CustomerID] [int] NOT NULL,
    [CustomerStoreID] [int] NOT NULL,
    [CustomerItemDescription] [nvarchar](50) NOT NULL,

    CONSTRAINT [PK_CustomerItem] 
    PRIMARY KEY CLUSTERED([CustomerItemID] ASC)
   ) ON [PRIMARY]
GO

INSERT INTO [dbo].[Customer]([CustomerID], [Name], [Surname])
   SELECT 1, N'John ', N'Smith' UNION ALL
   SELECT 2, N'Mark', N'Bloggs' UNION ALL
   SELECT 3, N'Richard', N'Lay'

INSERT INTO [dbo].[CustomerItem]([CustomerItemID], [CustomerID], [CustomerStoreID], [CustomerItemDescription])
   SELECT 1, 1, 1, N'BookOne' UNION ALL
   SELECT 2, 1, 1, N'BookTwo' UNION ALL
   SELECT 3, 1, 2, N'BookThree'UNION ALL
   SELECT 4, 1, 2, N'BookFour' UNION ALL
   SELECT 5, 2, 2, N'BookFive'UNION ALL
   SELECT 6, 2, 2, N'BookSix' UNION ALL
   SELECT 7, 3, 3, N'BookSeven' UNION ALL
   SELECT 8, 3, 3, N'BookEight'
GO

IF EXISTS (SELECT * FROM DBO.SYSOBJECTS WHERE id = OBJECT_ID(N'[dbo].[DeleteCustomerAndItemsByStoreId]') AND OBJECTPROPERTY(id, N'IsProcedure') = 1)
   DROP PROCEDURE [dbo].[DeleteCustomerAndItemsByStoreId]
GO

CREATE PROCEDURE DeleteCustomerAndItemsByStoreId
                   @CustomerStoreID INT
/*
   Delete all customerItems  based on @CustomerStoreID
   Delete the customer itself when he not longer has customerItems
*/
AS
   DELETE FROM CustomerItem 
   WHERE CustomerStoreID = @CustomerStoreID

   ---Loop through the customer table and  Delete Customer if no longer has children
   --???
   COMMIT

Basically when processing/deleting the last customerItem also delete the customer.

Stored procedure will only have one parameter @CustomerStoreID

Answer 1

delete from Customer where CustomerID in
(select distinct CustomerID 
 from customer c left outer join CustomerItem i 
  on c.CustomerID = i.CustomerID
 where i.CustomerID is null)