Question

MSSQL 2005 .I want to get a lock on a table at the start of transaction and only release it at the end of the transaction

BEGIN TRANSACTION;
-- get lock
BEGIN TRY
END TRY
BEGIN CATCH
    IF @@TRANCOUNT > 0 BEGIN
        ROLLBACK TRANSACTION; 
        -- release lock
    END
END CATCH;

IF @@TRANCOUNT > 0 BEGIN
    COMMIT TRANSACTION;
    -- release lock
END
GO 

Does lock on table gets automatically released once transaction has completed or rolledback?

Answer 1

Table locks, or other types of locks, can be set using hints like so:

UPDATE Users WITH (TABLOCK) SET Username = 'fred' WHERE Username = 'foobar'

Locks will generally expire when the command completes (even if the transaction is not yet done), unless you add other hints to keep them around within the scope of the transaction. See http://msdn.microsoft.com/en-us/library/ms187373%28v=sql.90%29.aspx for an explanation of all lock types and other table hints.

Locks will affect other users depending on the isolation level of their own transactions. See http://msdn.microsoft.com/en-us/library/ms173763%28v=sql.90%29.aspx for more info.