You may use the IF, THEN, ELSE, ELSIF, and END IF keywords in PL/SQL for performing conditional logic. The following syntax illustrates the use of conditional logic:
IF condition1 THEN statements1 ELSIF condition2 THEN statements2 ELSE statements3 END IF;
where
condition1 and condition2 are Boolean expressions that evaluate to true or false.
statements1 , statements2 , and statements3 are PL/SQL statements.
This conditional logic flows as follows :
If condition1 is true, then statements1 is executed.
If condition1 is false but condition2 is true, then statements2 is executed.
If neither condition1 nor condition2 are true, then statements3 is executed.
You can also embed IF statements within another IF statement, as shown in the following example:
IF count > 0 THEN message := 'count is positive'; IF area > 0 THEN message := 'count and area are positive'; END IF ELSIF count = 0 THEN message := 'count is zero'; ELSE message := 'count is negative'; END IF;