The IF statement causes a statement to be executed or not executed based on the value of a Boolean expression.

<if statement>

──<if clause>──<statement>─┬─────────────────────┬─────────────────────┤
                           └─ ELSE ──<statement>─┘

<if clause>

── IF ──<Boolean expression>── THEN ───────────────────────────────────┤