Question

My code does not update the thread field. It is null. Anyone have any ideas?

INSERT INTO [Messages]([Sender], [Receiver], [Job_Number], [Subject], [MessageText], [DateSent])
VALUES(@Sender, @Receiver, @Job_Number, @Subject, @MessageText, @DateSent)

SET @ThreadID = SCOPE_IDENTITY()

UPDATE [Messages] 
SET Thread = @ThreadID
WHERE MessageID = @ThreadID

EDIT:
It seems the UPDATE routine isn’t being executed at all. I even added the following code to the end of the sproc, but nothing gets updated.

UPDATE Comments 
SET SomeField = @ThreadID
where SCID = 33

EDIT:

/****** Object:  Table [dbo].[Messages]    Script Date: 04/09/2010 12:08:55 ******/
SET ANSI_NULLS ON
GO

SET QUOTED_IDENTIFIER ON
GO

SET ANSI_PADDING ON
GO

CREATE TABLE [dbo].[Messages](
    [MessageID] [int] IDENTITY(1,1) NOT NULL,
    [Sender] [varchar](30) NOT NULL,
    [Receiver] [varchar](30) NOT NULL,
    [Job_Number] [varchar](20) NULL,
    [Subject] [varchar](200) NULL,
    [MessageText] [varchar](max) NULL,
    [DateSent] [datetime] NULL,
    [Thread] [int] NULL,
 CONSTRAINT [PK_Messages] PRIMARY KEY CLUSTERED 
(
    [MessageID] 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

SET ANSI_PADDING OFF
GO

ALTER TABLE [dbo].[Messages] ADD  CONSTRAINT [DF_Messages_DateSent]  DEFAULT (getdate()) FOR [DateSent]
GO

EDIT:
When I execute the stored procedure from Management Studio, the update works just fine. The problem is in my app when I call it using SQLHelper:

SqlHelper.ExecuteNonQuery(ConfigurationManager.ConnectionStrings["Conn"].ConnectionString,
            "spMessagesInsert",
            0,
            message.Sender, 
            message.Receiver,
            message.Job_Number,
            message.Subject,
            message.MessageText,
            message.DateSent
            );

EDIT: Ultimately, I changed the program code to call the stored procedure using Linq-to-sql instead of using SqlHelper. This seemed to fix the issue.

Answer 1

“When you eliminate the impossible,
whatever is left, however improbable,
must be the truth”

There are only a handful of possibilities if we assume that there are no errors:

1. The value is not being inserted or deleted. We can verify that by querying for it right after Set @ThreadId = SCOPE_IDENTITY()
2. The Insert transaction is being rolled (e.g. from calling code transaction, from a calling sp transaction). We can verify that by looking at @@TRANCOUNT before and after the Update statement.
3. Something is setting the Thread column to null right after your Update statement. We can check @@ROWCOUNT right after the Update statement. If it is zero, then the only possibility is that the record no longer exists. If it is 1, then clearly the update worked. Right after the Update statement, you should be able to call Select * From Messages Where MessageId = @ThreadId And Thread Is Not Null and get a record. That means if later in your code is Null again, something else had changed it.

Try the following:

Set NoCount Off

INSERT INTO [Messages]([Sender], [Receiver], [Job_Number], [Subject], [MessageText], [DateSent])

VALUES(@Sender, @Receiver, @Job_Number, @Subject, @MessageText, @DateSent)

SET @ThreadID = SCOPE_IDENTITY()

-- ensure that the value is not null
Select @ThreadId

-- we should get our record from this query
Select * From Messages Where MessageId = @ThreadId

UPDATE [Messages] 
SET Thread = @ThreadID
WHERE MessageID = @ThreadID

-- we should get 1
Select @@ROWCOUNT

-- we should get a value
Select * From Messages Where MessageId = @ThreadId And Thread Is Not Null

-- are we in a transaction?
Select @@TRANCOUNT

EDIT
One other immensely helpful tool in rooting out these sorts of problems is the SQL Server Profiler. For example, you can tell it to show Rollback Tran completed or Commit Tran completed events along with the other SQL statements and see if something is rolling back the transaction.