插入语句与外键约束冲突-SQL Server 2012

Question

I have 3 tables : Application, Control and Application Control which is basically a many to many relationship between Application and Control.

App table

App_ID int (PK)
.....

ApplicationControl table

FK_APP_ID int (PK)
FK_Controls_ID (PK)

and Control table

ID int (PK)
Name varchar(50)     

Both App and Control tables are populated with some entries. When I try to insert an entry in the ApplicationControl table (taking an id from App and an ID from Control) it says:

The Insert statement conflicted with the FOREIGN KEY constraint 
(between ApplicationControl and Control) The conflict occured in table Control,
column ID. 

Any ideas why? It can insert the Application ID but It can't insert the Control ID and there aren't any differences between these two relations.

USE [PicknickDB]
GO

/****** Object:  Table [dbo].[ApplicationControl]    Script Date: 7/10/2013 3:21:29 PM  ******/ 
SET ANSI_NULLS ON
GO

SET QUOTED_IDENTIFIER ON
GO

CREATE TABLE [dbo].[ApplicationControl](
[FK_App_ID] [int] NOT NULL,
[FK_Controls_ID] [int] NOT NULL,
CONSTRAINT [PK_ApplicationControl] PRIMARY KEY CLUSTERED 
(
[FK_App_ID] ASC,
[FK_Controls_ID] ASC
 )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF,      ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
 ) ON [PRIMARY]

 GO

 ALTER TABLE [dbo].[ApplicationControl]  WITH CHECK ADD  CONSTRAINT       [FK_MapAppControls_Applications] FOREIGN KEY([FK_App_ID])
REFERENCES [dbo].[Application] ([App_ID])
ON UPDATE CASCADE
ON DELETE CASCADE
GO

ALTER TABLE [dbo].[ApplicationControl] CHECK CONSTRAINT   [FK_MapAppControls_Applications]
GO

ALTER TABLE [dbo].[ApplicationControl]  WITH CHECK ADD  CONSTRAINT [FK_MapAppControls_Controls] FOREIGN KEY([FK_App_ID])
REFERENCES [dbo].[Control] ([ID])
ON UPDATE CASCADE
ON DELETE CASCADE
GO

ALTER TABLE [dbo].[ApplicationControl] CHECK CONSTRAINT [FK_MapAppControls_Controls]
GO

Answer 1

ALTER TABLE [dbo].[ApplicationControl]  WITH CHECK ADD  CONSTRAINT 

[FK_MapAppControls_Controls] FOREIGN KEY([FK_App_ID]) --Really?

REFERENCES [dbo].[Control] ([ID])
ON UPDATE CASCADE
ON DELETE CASCADE

So, FK_App_ID is used as a reference to both the Application and the Control table?

I'd suggest that that should be FK_Controls_ID instead.

Answer 2

In cases like this it is best to turn on Profiler and see exactly what values it is trying to insert. This may lead to seeing why there is a problem. My most likely guess is that the value being sent to the insert for the second table is NULL because the code forgot to set it somehwere.