Question

Question 5 (Marks: 15) Q.5.1 The IF Statement is the most commonly used control-flow statement. Discuss any (10) two of the three forms of IF Statements supported by Oracle. Demonstrate your understanding by giving examples. Q.5.2 Write an if statement that prevents a user from entering an invoice amount that is (5) less than zero (0). Display an appropriate error message to the user.

Answer 1

Q. 5.1

There are three forms of IF statements: IF-THEN, IF-THEN-ELSE, and IF-THEN-ELSIF.

The IF statement associates a Boolean value with a sequence of statements enclosed by the keywords THEN and END IF. The sequence of statements is executed only if the boolean value returns TRUE. If the value returns FALSE or NULL, the IF statement does nothing.

The second form of IF statement adds the keyword ELSE followed by an alternative sequence of statements. The sequence of statements in the ELSE clause is executed only if the Boolean value in IF returns FALSE or NULL. By using ELSE it is ensured that a series of statements is executed in either case.

Q.5.2

DECLARE
   invoice_amount NUMBER;

BEGIN

invoice_amount := &enter_value;

IF invoice_amount < 0 THEN
      RAISE_APPLICATION_ERROR(-20021,
        'execute_sql: Negative value entered.  
         Status = ' || status);
    END IF;

END;

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