Question

I need to get the last inserted row in a specific table for strictly the current session. I can’t use @@IDENTITY and SCOPE_IDENTITY() as they will return the last inserted identity for ANY table. The problem with IDENT_CURRENT is that it will return the last inserted identity of a record for a specific table but for ANY session. This is a problem for me because the INSERT is called by multiple sessions, and I specifically need the identity of the last inserted record for my specific session.

Any pointers how to accomplish this?

ps. the INSERT statement is not inside a SPROC, so SPROC solutions are not viable.

Thanks

Answer 1

I know it’s not the answer you seem to want to hear, but the answer is to use SCOPE_IDENTITY(). The problem you are thinking of (where it will be for any table) is why we use SCOPE_IDENTITY() instead of @@IDENTITY. Consider the case where you have a table with an IDENTITY column, and an insert trigger on that table that itself inserts into a table with an IDENTITY column.

CREATE TABLE dbo.Log(LogID INT IDENTITY(100,1), FooID INT);

CREATE TABLE dbo.Foo(FooID INT IDENTITY(1,1), name VARCHAR(32));
GO

CREATE TRIGGER dbo.Foo_Insert
ON dbo.Foo
FOR INSERT
AS
BEGIN
  SET NOCOUNT ON;
  INSERT dbo.Log(FooID) SELECT FooID FROM inserted;
END
GO

Now, your situation is that you want a reliable way to retrieve the ID after an insert. SCOPE_IDENTITY() gives you that, since it is restricted to your scope, while @@IDENTITY is not restricted to your scope (meaning it will grab the last IDENTITY issued, which happened in the triggers’ scope, not your scope:

INSERT dbo.Foo(name) SELECT 'Bob';

SELECT
  @@IDENTITY,
  SCOPE_IDENTITY();

Results:

----  ----
100   1

Note that neither SCOPE_IDENTITY() nor @@IDENTITY should be used in the case where you insert multiple rows. The way to do this would be to use the OUTPUT clause. First let’s drop the trigger:

DROP TRIGGER dbo.Foo_Insert;

Now let’s test a multi-row insert:

  INSERT dbo.Foo(name) 
    OUTPUT inserted.FooID, inserted.name
    SELECT 'Frank' UNION ALL SELECT 'Jim';

Results:

FooID  name
-----  -----
2      Frank
3      Jim

If you have conditional inserts, there is no difference. Keeping the tables we have, let’s try this code twice:

DECLARE @table SYSNAME;
SET @table = N'Log';

IF @table = N'Log'
BEGIN
    INSERT dbo.Log(FooID) SELECT 10;
END

IF @table = N'Foo'
BEGIN
    INSERT dbo.Foo(name) SELECT 'Tom';
END

SELECT SCOPE_IDENTITY();

Result:

----
101

Let’s try it again with N'Foo':

DECLARE @table SYSNAME;
SET @table = N'Foo';

IF @table = N'Log'
BEGIN
INSERT dbo.Log(FooID) SELECT 10;
END

IF @table = N'Foo'
BEGIN
    INSERT dbo.Foo(name) SELECT 'Tom';
END

SELECT SCOPE_IDENTITY();

Results:

----
4

If it’s more complex than that (e.g. you may insert into more than one table), you can do something like:

IF <some conditional>
BEGIN
    INSERT dbo.sometable ...
    SET @somevar = SCOPE_IDENTITY();
END
IF <some other conditional>
BEGIN
    INSERT dbo.some_other_table ...
    SET @some_other_var = SCOPE_IDENTITY();
END

I’m not sure why you think this doesn’t work, and I’m not sure why I have to go to this length to convince you that it does. Again, if you show an example where this doesn’t work (or what “ANY table” you think might interfere), we might be able to comment. As it stands it sounds like your opinion of SCOPE_IDENTITY() is based on something you’ve heard about @@IDENTITY. These assumptions are quite easy to prove or disprove yourself.

As an aside, IDENT_CURRENT should not even be mentioned in this conversation. It is not safe to use for concurrent activity at all, and you should pretend that you’ve never heard of it as far as I’m concerned. You should also consider the same for @@IDENTITY – I can’t think of a valid use for it unless you really do want to capture, from outside of the trigger, the IDENTITY generated inside a trigger.