Introduction to Transactions

Transaction - a sequence of operations performed as a single logical unit of work.

ACID
Atomic - all the work in the transaction is treated as a single unit. Either it is all performed or none of it is.
Consistent – a completed transaction leaves the database in a consistent internal state.
Isolations – the transaction sees the database in a consistent state. This transaction operates on a consistent view of the data. If two transactions try to update the same table, one will go first and then the other will follow.
Durability - the results of the transaction are permanently stored in the system.

Multi-Statement Transactions

BEGIN TRAN

UPDATE 	...
SET	... = ''
WHERE	... = '...'

UPDATE 	...
SET	... = ''
WHERE	... = '...'

COMMIT TRAN

Rolling Back

BEGIN TRAN

UPDATE 	...
SET	... = ''
WHERE	... = '...'

UPDATE 	...
SET	... = ''
WHERE	... = '...'

IF @@ROWCOUNT = 5
  COMMIT TRAN
ELSE
  ROLLBACK TRAN

Stored Procedures

CREATE PROCEDURE TranTest1
AS
BEGIN TRAN

INSERT INTO [...]
([f1], [f2], [f3], [f4], [f5])
VALUES	('...', '...', '...', '...', ...)

UPDATE 	...
SET	... = ''
WHERE	... = '...'

COMMIT TRAN
GO

Source

A = Single Unit of Work
C = Consistent Internal DB State
I =
D =