Section 4 Lesson 2: Conditional Control: Case Statements

Conditional Control: Case Statements

 Section 1
   
  1.  How must you end a CASE expression? (1) Points
     
    END; (*)
    ENDIF;
    END CASE;
    ENDCASE;
     
  2.  Examine the following code:
DECLARE
   v_a BOOLEAN;
   v_b BOOLEAN := FALSE;
   v_c BOOLEAN ;
BEGIN
   v_c := (v_a AND v_b);
   -- Line A
    ....
END;

What is the value of V_C at Line A?
(1) Points
     
    True
    False (*)
    NULL
    Undefined
     
  3.  What will be displayed when the following block is executed?
DECLARE
   v_age1 NUMBER(3);
   v_age2 NUMBER(3);
   v_message VARCHAR2(20);
BEGIN
   CASE
     WHEN v_age1 = v_age2 THEN v_message := 'Equal';
     WHEN v_age1 <> v_age2 THEN v_message := 'Unequal';
     ELSE v_message := 'Undefined';
   END CASE;
   DBMS_OUTPUT.PUT_LINE(v_message);
END;
(1) Points
     
    Equal
    Undefined (*)
    Unequal
    Nothing will be displayed because V_MESSAGE is set to NULL.
     
  4.  Examine the following code:
DECLARE
   v_score NUMBER(3);
   v_grade CHAR(1);
BEGIN
   v_grade := CASE v_score
   -- Line A
   ....

The CASE expression must convert a numeric score to a letter grade: 90 -> A, 80 -> B, 70 -> C and so on. What should be coded at Line A?
(1) Points
     
    WHEN 90 THEN grade := 'A'
    WHEN 90 THEN v_grade := 'A';
    WHEN 90 THEN 'A' (*)
    WHEN 90 THEN 'A';
     
  5.  What will be displayed when the following block is executed?
DECLARE
   v_age NUMBER(3);
   v_gender VARCHAR2(6) := 'Female';
   v_status VARCHAR2(20);
BEGIN
   CASE
     WHEN v_age >= 18 AND v_gender = 'Male' THEN v_status := 'Adult Male';
     WHEN v_age >= 18 AND v_gender = 'Female' THEN v_status := 'Adult Female';
     WHEN v_age < 18 AND v_gender = 'Male' THEN v_status := 'Junior Male';
     WHEN v_age < 18 AND v_gender = 'Female' THEN v_status := 'Junior Female';
     ELSE v_status := 'Other Value';
   END CASE;
   DBMS_OUTPUT.PUT_LINE(v_status);
END;
(1) Points
     
    Adult Male
    Junior Female
    Other Value (*)
    Nothing will be displayed because V_STATUS is set to NULL.
     
  6.  How must you end a CASE statement? (1) Points
     
    END;
    END CASE; (*)
    END IF;
    ENDCASE;
     
  7.  Examine the following code:
DECLARE
  v_score NUMBER(3);
  v_grade CHAR(1);
BEGIN
  CASE v_score
  -- Line A
  ....

The CASE statement must convert a numeric score to a letter grade: 90 -> A, 80 -> B, 70 -> C and so on.
What should be coded at Line A?
(1) Points
     
    WHEN 90 THEN v_grade := 'A'
    WHEN 90 THEN v_grade := 'A'; (*)
    WHEN 90 THEN 'A'
    WHEN 90 THEN 'A';
     
  8.  Look at the following code:
DECLARE
   x BOOLEAN := FALSE;
   y BOOLEAN := FALSE;
   z BOOLEAN ;
BEGIN
   z := (x OR NOT y);
   -- Line A
   ....
END;
What is the value of Z at Line A?
(1) Points
     
    True (*)
    False
    NULL
    An error will occur because you cannot combine two Boolean variables using "NOT".