Lab 7.1 Exercise Answers
This section gives you some suggested answers to the questions in Lab 7.1, with discussion related to how those answers resulted. The most important thing to realize is whether your answer works. You should figure out the implications of the answers here and what the effects are from any different answers you may come up with.7.1.1 Answers
A1:
| Answer: The first version of the output is produced when the value of v_num is equal to 4. Your output should look like the following: Enter value for sv_num: 4
old 2: v_num NUMBER := &sv_num;
new 2: v_num NUMBER := 4;
Square root of 4 is 2
PL/SQL procedure successfully completed.
The second version of the output is produced when v_num is equal to -4. Your output should look like the following: Enter value for sv_num: -4
old 2: v_num NUMBER := &sv_num;
new 2: v_num NUMBER := -4;
An error has occurred
PL/SQL procedure successfully completed.
| A2:
| Answer: Error message "An error has occurred" was generated for the second run of example because a runtime error has occurred. The built-in function SQRT is unable to accept a negative number as its argument. Therefore, the exception VALUE_ERROR was raised, and the error message was displayed on the screen. | A3:
| Answer: The new version of the program should look similar to the program below. All changes are shown in bold letters. -- ch07_1b.sql, version 2.0
SET SERVEROUTPUT ON;
DECLARE
v_num NUMBER := &sv_num;
BEGIN
IF v_num >= 0 THEN
DBMS_OUTPUT.PUT_LINE ('Square root of '||v_num||
' is '||SQRT(v_num));
ELSE
DBMS_OUTPUT.PUT_LINE ('A number cannot be negative');
END IF;
END;
|
Notice that before you calculate the square root of a number, you can check to see if the number is greater than or equal to 0 with the help of the IF-THEN-ELSE statement. If the number is negative, the message "A number cannot be negative" is displayed on the screen. When the value of -4 is entered for the variable v_num, this script produces the following output:Enter value for sv_num: -4
old 2: v_num NUMBER := &sv_num;
new 2: v_num NUMBER := -4;
A number cannot be negative
PL/SQL procedure successfully completed.
|
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