Flow Control

T-SQL can be considered a programming language because we can add conditional logic to our T-SQL queries. In other words, T-SQL supports the IF…ELSE construct, like the majority of procedural programming languages.

Syntax

The IF…ELSE construct has this syntax in T-SQL:

IF [Condition]
BEGIN
    [Actions to perform if the condition is true]
END
ELSE
BEGIN
    [Actions to perform if the condition is false]
END

The [Condition] in the snippet above is any expression that returns a boolean value (true or false). If we do not need to handle situations when the [Condition] is false, then we can safely omit the ELSE block:

IF [Condition]
BEGIN
    [Actions to perform if the condition is true]
END

Example

We have the @Age variable of type INT, which stores the user’s age. If it is below 21, we’ll print 'Not allowed'. Otherwise, we’ll output 'Access granted':