What happens here? SQL Server - XACT_ABORT ON + @@ERROR Checking . .

What happens with this type of scenario?

SET XACT_ABORT ON

BEGIN TRANSACTION

    ---DO SOME开发者_如何学PythonTHING HERE THAT CAUSES AN ERROR

COMMIT TRANSACTION

if @@error != 0
raiserror('SP failed. Step 7.', 20, -1) with log GO

My guess is that because XACT_ABORT is ON the COMMIT TRANSACTION never happens (because the whole thing is rolled back and terminated), and neither does the last statement (checking for @@error and then calling raiseerror).

Correct.

SET XACT_ABORT jumps out of the batch. Your IF is part of the same batch.

If you want some processing on error, then use BEGIN TRY etc

SET XACT_ABORT ON
BEGIN TRY
BEGIN TRANSACTION

    ---DO SOMETHING HERE THAT CAUSES AN ERROR

COMMIT TRANSACTION
END TRY
BEGIN CATCH
    raiserror('SP failed. Step 7.', 20, -1) with log
END CATCH
GO

I'm also intrigued by severity 20 because it breaks the connection. Usually you'd use 16 which is user defined error.