Prentice Hall Oracle Plsql By Example 3Rd Edition [Electronic resources] نسخه متنی

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.

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.

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;