How to solve "Self referencing table conflicted with the FOREIGN KEY constraint" - sql

Question

I am creating a simple table with automatically generated employee id with a prefix like
sale_900000,sale_900001,sale_900002,sale_900003
It is a self-referencing table.
When I insert data into the table I get errors like this:
*Msg 547, Level 16, State 0, Procedure tr_generate_emp_id, Line 42
The INSERT statement conflicted with the FOREIGN KEY SAME TABLE constraint "Registration_Registration". The conflict occurred in database "test", table "dbo.Registration", column 'empid'.*
For automatic employee id I am using an instead of insert trigger on the table
This is my table
CREATE TABLE [dbo].[Registration](
[empid] [varchar](40) NOT NULL,
[id] [int] IDENTITY(900000,1) NOT NULL,
[First_Name] [varchar](40) NULL,
[Last_Name] [varchar](40) NULL,
[Address] [varchar](40) NULL,
[E_Mail] [varchar](40) NULL,
[Country] [varchar](40) NULL,
[Mobile_No] [varchar](40) NULL,
[Designation] [varchar](40) NULL,
[managerID] [varchar](40) NULL,
CONSTRAINT [PK_Registration] PRIMARY KEY CLUSTERED
(
[empid] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]
ALTER TABLE [dbo].[Registration] WITH CHECK ADD CONSTRAINT [Registration_Registration] FOREIGN KEY([managerID])
REFERENCES [dbo].[Registration] ([empid])
and this is my trigger
ALTER TRIGGER [dbo].[tr_generate_emp_id] ON [dbo].[Registration]
INSTEAD OF INSERT
AS
BEGIN
DECLARE #id INT
DECLARE #id1 INT
DECLARE #id_s VARCHAR(50)
DECLARE #empid VARCHAR(50)
DECLARE #First_Name VARCHAR(50)
DECLARE #Last_Name VARCHAR(50)
DECLARE #Address VARCHAR(50)
DECLARE #E_Mail VARCHAR(50)
DECLARE #Country VARCHAR(50)
DECLARE #Mobile_No VARCHAR(50)
DECLARE #Designation VARCHAR(50)
DECLARE #managerID VARCHAR(50)
SELECT #id = Id
FROM dbo.Registration
IF #id IS NULL
SET #id = 899999
SET #id1 = #id + 1
SELECt #First_Name = First_Name ,
#Last_Name = Last_Name ,
#Address = Address ,
#E_Mail = E_Mail ,
#Country = Country ,
#Mobile_No = Mobile_No ,
#Designation = Designation ,
#managerID = managerID
FROM INSERTED
SET #id_s = CONVERT(VARCHAR(50), #id1)
SET #empid = 'Sale_' + #id_s
INSERT INTO dbo.Registration
( empid ,
First_Name ,
Last_Name ,
Address ,
E_Mail ,
Country ,
Mobile_No ,
Designation ,
managerID
)
VALUES ( #empid , -- empid - varchar(40)
#First_Name , -- First_Name - varchar(40)
#Last_Name , -- Last_Name - varchar(40)
#Address , -- Address - varchar(40)
#E_Mail , -- E_Mail - varchar(40)
#Country, -- Country - varchar(40)
#Mobile_No , -- Mobile_No - varchar(40)
#Designation , -- Designation - varchar(40)
#managerID -- managerID - varchar(40)
)
END
i am inserting
INSERT INTO dbo.Registration
( empid ,
First_Name ,
Last_Name ,
Address ,
E_Mail ,
Country ,
Mobile_No ,
Designation ,
managerID
)
VALUES ( '' , -- empid - varchar(40)
'admin' , -- First_Name - varchar(40)
'jon' , -- Last_Name - varchar(40)
's-24' , -- Address - varchar(40)
'abc#gmail.com' , -- E_Mail - varchar(40)
'india' , -- Country - varchar(40)
'098735322211' , -- Mobile_No - varchar(40)
'manager' , -- Designation - varchar(40)
'' -- managerID - varchar(40)
)
and error
Msg 547, Level 16, State 0, Procedure tr_generate_emp_id, Line 42
The INSERT statement conflicted with the FOREIGN KEY SAME TABLE constraint "Registration_Registration". The conflict occurred in database "test", table "dbo.Registration", column 'empid'.
The statement has been terminated.

Answer 1

The main issue is that you're doing this in the first place. I just read through your trigger. Just changed empid to be a computed field...
CREATE TABLE [dbo].[Registration](
[empid] AS ('Sale_' + Convert(Varchar(50),id)) PERSISTED,
[id] [int] IDENTITY(900000,1) NOT NULL,
[First_Name] [varchar](40) NULL,
[Last_Name] [varchar](40) NULL,
[Address] [varchar](40) NULL,
[E_Mail] [varchar](40) NULL,
[Country] [varchar](40) NULL,
[Mobile_No] [varchar](40) NULL,
[Designation] [varchar](40) NULL,
[managerID] [varchar](40) NULL,
CONSTRAINT [PK_Registration] PRIMARY KEY CLUSTERED
(
[empid] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]

Answer 2

In your trigger I think this line
SELECT #id = Id
is meant to read
SELECT #id = MAX(Id)
I'm surprised you havent received PK violation errors as a result. The FK violation error can only be due to trying to insert MangerId value that doesn't match an empid value (as far as I can see from the code). So check what managerId value you are supplying.

Answer 3

Check your Nest Level.
http://msdn.microsoft.com/en-us/library/ms182737(v=sql.100).aspx
I would put this value in a (dbo.) AuditTable, something that has nothing to do with your primary table.
trigger_nestlevel()
Change from Row Based to Set Based Logic.

Answer 4

I re-did your trigger to be set based but I think #Love2Learn may have a better solution for you.
ALTER TRIGGER [dbo].[tr_generate_emp_id] ON [dbo].[Registration]
INSTEAD OF INSERT
AS
BEGIN
DECLARE #id INT
-- Get the last id used.
SELECT #id = MAX(Id)
FROM dbo.Registration
IF #id IS NULL
SET #id = 899999
WITH MyInserted AS (SELECT
ROW_NUMBER() OVER(ORDER BY E_Mail) AS rownum-- Email is just a random order by here. Could be anything you want.
,*
FROM inserted)
INSERT INTO dbo.Registration
( empid ,
First_Name ,
Last_Name ,
Address ,
E_Mail ,
Country ,
Mobile_No ,
Designation ,
managerID
)
SELECT -- add the last id used with the rownum (ranges from 1 to num of rows)
'Sale_'+CONVERT(VARCHAR(50), #id+rownum) -- empid - varchar(40)
First_Name, -- First_Name - varchar(40)
Last_Name, -- Last_Name - varchar(40)
Address, -- Address - varchar(40)
E_Mail, -- E_Mail - varchar(40)
Country, -- Country - varchar(40)
Mobile_No, -- Mobile_No - varchar(40)
Designation, -- Designation - varchar(40)
ManagerID -- managerID - varchar(40)
FROM MyInserted
END