Control-of-flow keywords help SQL Server determine when and how Transact-SQL statements should execute. With these keywords, you can add logic around and within Transact-SQL statements to control program execution. Control-of-flow keywords add greater flexibility in OLTP application design and help you write clever code. Control-of-flow keywords include BEGIN…END, IF…ELSE, CASE, WHILE, BREAK, CONTINUE, RETURN, GOTO, and WAITFOR.
The BEGIN…END keywords identify a code block. We typically use them to group Transact-SQL statements. The BEGIN…END blocks can be nested. We also use BEGIN…END statements to identify a code block in an IF…ELSE clause, WHILE loop, and CASE element. The following is the basic syntax for the BEGIN…END keyword block:
BEGIN
{
sql_statement | statement_block
}
ENDThe following is a basic example of BEGIN…END:
USE [AdventureWorks2012];
GO
BEGIN
DECLARE @Today [datetime];
SET @Today = CURRENT_TIMESTAMP;
...