SQL Server - Nested transactions in a stored procedure

Question

Lets say this is the situation:

  [Stored Proc 1]
  BEGIN
     BEGIN TRANSACTION
       ...
            exec sp 2   
     COMMIT
  END

Now, if SP 2 - rolls back for whatever reason, does SP 1 - commit or rollback or throw exception?

Thanks.

Answer 1

It is possible for the work done by SP2 to be rolled back and not loose the work done by SP1. But for this to happen, you must write your stored procedures using a very specific pattern, as described in Exception handling and nested transactions:

create procedure [usp_my_procedure_name]
as
begin
    set nocount on;
    declare @trancount int;
    set @trancount = @@trancount;
    begin try
        if @trancount = 0
            begin transaction
        else
            save transaction usp_my_procedure_name;

        -- Do the actual work here

lbexit:
        if @trancount = 0   
            commit;
    end try
    begin catch
        declare @error int, @message varchar(4000), @xstate int;
        select @error = ERROR_NUMBER(), @message = ERROR_MESSAGE(), @xstate = XACT_STATE();
        if @xstate = -1
            rollback;
        if @xstate = 1 and @trancount = 0
            rollback
        if @xstate = 1 and @trancount > 0
            rollback transaction usp_my_procedure_name;

        raiserror ('usp_my_procedure_name: %d: %s', 16, 1, @error, @message) ;
    end catch   
end

Not all errors are recoverable, there are a number of error conditions that a transaction cannot recover from, the most obvious example being deadlock (your are notified of the deadlock exception after the transaction has already rolled back). Both SP1 and SP@ have to be written using this pattern. If you have a rogue SP, or you want to simple leverage existing stored procedures that nilly-willy issue ROLLBACK statements then your cause is lost.