Chapter 5 Test Your Thinking

In this chapter you learned about different types of IF statements. You also learned that all of these different IF statements can be nested one inside another. Here are some exercises that will help you test the depth of your understanding.

1)	Rewrite ch05_1a.sql. Instead of getting information from the user for the variable v_date , define its value with the help of the function SYSDATE. After it has been determined that a certain day falls on the weekend , check to see if the time is before or after noon. Display the time of the day together with the day.
2)	Create a new script. For a given instructor, determine how many sections he or she is teaching. If the number is greater than or equal to 3, display a message saying that the instructor needs a vacation. Otherwise, display a message saying how many sections this instructor is teaching.
3)	Execute the two PL/SQL blocks below and explain why they produce different output for the same value of the variable v_num. Remember to issue the SET SERVEROUTPUT ON command before running this script. -- Block 1 DECLARE v_num NUMBER := NULL; BEGIN IF v_num > 0 THEN DBMS_OUTPUT.PUT_LINE ('v_num is greater than 0'); ELSE DBMS_OUTPUT.PUT_LINE ('v_num is not greater than 0'); END IF; END; -- Block 2 DECLARE v_num NUMBER := NULL; BEGIN IF v_num > 0 THEN DBMS_OUTPUT.PUT_LINE ('v_num is greater than 0'); END IF; IF NOT (v_num > 0) THEN DBMS_OUTPUT.PUT_LINE ('v_num is not greater than 0'); END IF; END;

The projects in this section are meant to have you utilize all of the skills that you have acquired throughout this chapter. The answers to these projects can be found in Appendix D and at the companion Web site to this book, located at http://authors.phptr.com/rosenzweig3e. Visit the Web site periodically to share and discuss your answers.