-- To start with, verify @@TRANCOUNT is 0
SELECT @@TRANCOUNT
BEGIN TRAN A
-- Verify @@TRANCOUNT is 1
SELECT @@TRANCOUNT
-- Assume some real work happens here.
BEGIN TRAN B
-- verify @@TRANCOUNT is 2
SELECT @@TRANCOUNT
-- Assume some real work happens here
ROLLBACK TRAN B
-- @@TRANCOUNT is still 2, because the previous ROLLBACK
-- failed due to error 6401
SELECT @@TRANCOUNT
-- Assume some real work happens here
ROLLBACK TRAN A
-- This ROLLBACK succeeds, so @@TRANCOUNT is back to 0
SELECT @@TRANCOUNT
GO

-- To start with, verify @@TRANCOUNT is 0
SELECT @@TRANCOUNT
BEGIN TRAN A
-- Verify @@TRANCOUNT is 1
SELECT @@TRANCOUNT
-- Assume some real work happens here
BEGIN TRAN B
-- verify @@TRANCOUNT is 2
SELECT @@TRANCOUNT
-- Assume some real work happens here
ROLLBACK TRAN -- Notice the tran is unnamed, but works
-- That ROLLBACK terminates transaction. @@TRANCOUNT is now 0.
SELECT @@TRANCOUNT
-- The following ROLLBACK will fail because there is no open
-- transaction (that is, @@TRANCOUNT is 0)
ROLLBACK TRAN
-- @@TRANCOUNT does not go negative. It remains at 0.
SELECT @@TRANCOUNT
GO

-- To start with, verify @@trancount is 0
SELECT @@TRANCOUNT
BEGIN TRAN A
-- Verify @@TRANCOUNT is 1
SELECT @@TRANCOUNT
-- Assume some real work happens here
BEGIN TRAN B
-- Verify @@TRANCOUNT is 2
SELECT @@TRANCOUNT
-- Assume some real work happens here
COMMIT TRAN B
-- The COMMIT didn't COMMIT anything, but does decrement
-- @@TRANCOUNT
-- Verify @@TRANCOUNT is back down to 1:
SELECT @@TRANCOUNT
-- Assume some real work happens here
COMMIT TRAN A
-- The COMMIT on previous line does commit the changes and
-- closes the transaction
-- Since there's no open transaction, @@TRANCOUNT is again 0
SELECT @@TRANCOUNT
GO


-- To start with, verify @@TRANCOUNT is 0
SELECT @@TRANCOUNT
BEGIN TRAN A
-- Verify @@TRANCOUNT is 1
SELECT @@trancount
-- Assume some real work happens here
SAVE TRAN B
-- Verify @@TRANCOUNT is still 1. A savepoint does not affect it.
SELECT @@TRANCOUNT
-- Assume some real work happens here
ROLLBACK TRAN B
-- @@TRANCOUNT is still 1, because the previous ROLLBACK
-- affects just the savepoint, not the transaction
SELECT @@TRANCOUNT
-- Assume some real work happens here
ROLLBACK TRAN A
-- This ROLLBACK succeeds, so @@TRANCOUNT is back to 0
SELECT @@TRANCOUNT
GO