T-SQL EXEC and scope - sql

Question

Let's say I have a stored procedure with this in its body:
EXEC 'INSERT INTO ' + quotename(#table) ' blah...'
SELECT IDENT_CURRENT('' + #table + '')
Is IDENT_CURRENT() guaranteed to get the identity of that row INSERTed in the EXEC? IDENT_CURRENT() "returns the last identity value generated for a specific table in any session and any scope", but the scope is different within the EXEC than the stored procedure, right?
I want to make sure that if the stored procedure is being called multiple times at once, the correct identity is SELECTed.
EDIT: Or do I need to do both the INSERT and SELECT within the EXEC, like so:
declare #insert nvarchar
set #insert =
'INSERT INTO ' + quotename(#table) ' blah...' +
'SELECT IDENT_CURRENT(''' + #table + ''')'
EXEC #insert
And if that's the case, how do I SELECT the result of the EXEC if I want to continue with more code in T-SQL? Like this (although it's obviously not correct):
declare #insert nvarchar
set #insert =
'INSERT INTO ' + quotename(#table) ' blah...' +
'SELECT IDENT_CURRENT(''' + #table + ''')'
declare #ident int
set #ident = EXEC #insert
-- more code
SELECT * FROM blah
UPDATE: In the very first snippet, if I SELECT SCOPE_IDENTITY() instead of using IDENT_CURRENT(), NULL is returned by the SELECT. :(

Answer 1

Try
EXEC 'INSERT INTO ' + quotename(#table) ' blah...; SELECT ##IDENTITY'
or better, according to this
EXEC 'INSERT INTO ' + quotename(#table) ' blah...; SELECT SCOPE_IDENTITY()'

Answer 2

According to Microsoft's T-SQL docs:
IDENT_CURRENT is similar to the SQL
Server 2000 identity functions
SCOPE_IDENTITY and ##IDENTITY. All
three functions return last-generated
identity values. However, the scope
and session on which last is defined
in each of these functions differ:
IDENT_CURRENT returns the last
identity value generated for a
specific table in any session and any
scope.
##IDENTITY returns the last identity
value generated for any table in the
current session, across all scopes.
SCOPE_IDENTITY returns the last
identity value generated for any table
in the current session and the current
scope.
So I would say, no, IDENT_CURRENT does not guarantee to give you back the right value. It could be the last IDENTITY value inserted in a different session.
I would make sure to use SCOPE_IDENTITY instead - that should work reliably.
Marc

Answer 3

http://blog.sqlauthority.com/2009/03/24/sql-server-2008-scope_identity-bug-with-multi-processor-parallel-plan-and-solution/
There is a bug in SCOPE_IDENTITY() I have switched my stored procedures over to the methodology used to retrieve default values from an insert:
declare #TheNewIds table (Id bigint, Guid uniqueidentifier)
insert [dbo].[TestTable] output inserted.Id, inserted.Guid into #TheNewIds
values (default);
select #Id = [Id], #Guid = [Guid] from #TheNewIds;

Answer 4

I think Scope_Identity() is what you're looking for, which will give you the most recent identify in the current scope.

Answer 5

I'd like to chip in my favourite solution by using OUTPUT keyword. Since INSERT can support multiple rows at a time, we would want to know the identities inserted. Here goes:
-- source table
if object_id('Source') is not null drop table Source
create table Source
(
Value datetime
)
-- populate source
insert Source select getdate()
waitfor delay '00:00.1'
insert Source select getdate()
waitfor delay '00:00.1'
insert Source select getdate()
select * from Source -- test
-- destination table
if object_id('Destination') is null
create table Destination
(
Id int identity(1, 1),
Value datetime
)
-- tracking table to keep all generated Id by insertion of table Destination
if object_id('tempdb..#Track') is null
create table #Track
(
Id int
)
else delete #Track
-- copy source into destination, track the Id using OUTPUT
insert Destination output inserted.Id into #Track select Value from Source
select Id from #Track -- list out all generated Ids
Go ahead to run this multiple times to feel how it works.