Conditional statements are used to decide whether given conditions are met. Operations are executed based on the decisions made.
DWS supports five usages of IF:
IF_THEN is the simplest form of IF. If the condition is true, statements are executed. If it is false, they are skipped.
IF v_user_id <> 0 THEN UPDATE users SET email = v_email WHERE user_id = v_user_id; END IF;
IF-THEN-ELSE statements add ELSE branches and can be executed if the condition is false.
IF parentid IS NULL OR parentid = '' THEN RETURN; ELSE hp_true_filename(parentid); -- Call the stored procedure. END IF;
IF statements can be nested in the following way:
IF sex = 'm' THEN pretty_sex := 'man'; ELSE IF sex = 'f' THEN pretty_sex := 'woman'; END IF; END IF;
Actually, this is a way of an IF statement nesting in the ELSE part of another IF statement. Therefore, an END IF statement is required for each nesting IF statement and another END IF statement to end the parent IF-ELSE statement. To set multiple options, use the following form:
IF number_tmp = 0 THEN result := 'zero'; ELSIF number_tmp > 0 THEN result := 'positive'; ELSIF number_tmp < 0 THEN result := 'negative'; ELSE result := 'NULL'; END IF;
ELSEIF is an alias of ELSIF.
CREATE OR REPLACE PROCEDURE proc_control_structure(i in integer) AS BEGIN IF i > 0 THEN raise info 'i:% is greater than 0. ',i; ELSIF i < 0 THEN raise info 'i:% is smaller than 0. ',i; ELSE raise info 'i:% is equal to 0. ',i; END IF; RETURN; END; / CALL proc_control_structure(3); -- Delete the stored procedure: DROP PROCEDURE proc_control_structure;