The purpose of this week's lab is to work with basic PL/SQL syntax to create an anonymous block of code. In the lab, you will be using SQL*Plus to modify one of the tables in the MovieRental schema and then write a simple block of code to update the table with some new data and then execute the code in SQL*Plus. As an additional task in the lab, you will be asked to modify the existing PL/SQL block of code given to you to add exception handling and then execute it in SQL*Plus. Both of these concepts will help enforce the material covered in this second week.
For the lab, you will need to create a script file containing the PL/SQL code that will address the lab steps below. Run the script file in your SQL*Plus session using the SET ECHO ON session command at the beginning to capture both the PL/SQL block code and output from Oracle after the block of code has executed. To successfully test the code in Step 3, you will need to copy/paste your code into SQL*Plus for each movie ID as you change the value for the host variable. Spool your output to a file named with your last name plus lab 2 and give the file a text (.txt) extension. For example, if your last name was Johnson then the file would be named johnson_lab2.txt. Submit both the spooled output AND the script file for grading of the lab.
As business is becoming strong and the movie stock is growing for More Movie Rentals, the manager wants to do more inventory evaluations. One item of interest concerns any movie for which the company is holding $75 or more in value. The manager wants to focus on these movies in regards to their revenue generation to ensure the stock level is warranted. To make these stock queries more efficient, the application team decides that a column should be added to the MM_MOVIE table named STK_FLAG that will hold a value '*' if stock is $75 or more. Otherwise, the value should be NULL. Add the new column to the MM_MOVIE table as a CHAR data type.
Execute a DESC MM_MOVIE on the table both before you add the new column and after the column is added.
Note: Since this is code will be in your script file, you will need to comment it out after the first time you have execute the ALTER TABLE statement successfully to avoid getting errors each additional time your script file is run.
Create an anonymous block of PL/SQL code that contains a CURSOR FOR loop to accomplish the task described above in Step 1. Your loop will need to interrogate the value (using an IF statement) found in the movie_qty field of the cursor loop variable to see if it is >= 75. If this is true then you will need to update the new column in the table with an '*' WHERE CURRENT OF the table. If the quantity is not >= 75 (the ELSE side of the IF statement) then update the new column with a NULL.
Execute a SELECT * from MM_MOVIE both before and after you execute the new PL/SQL block of code to show that the process works.
Here is a block that retrieves the movie title and rental count based on a movie ID provided via a host variable.
SET SERVEROUTPUT ON
VARIABLE g_movie_id NUMBER
:g_movie_id := 4;
SELECT m.movie_title, COUNT(r.rental_id)
INTO v_title, v_count
FROM mm_movie m, mm_rental r
WHERE m.movie_id = r.movie_id
AND m.movie_id = :g_movie_id
GROUP BY m.movie_title;
DBMS_OUTPUT.PUT_LINE(v_title || ': ' || v_count);
Modify the block of code to add exception handlers for errors that you can and cannot anticipate. You will need to execute the entire code listing shown above each time you wish to test it by changing the value of :g_movie_id for each test.
Once finished, test your exception handling by running the modified block for the following values of :g_movie_id. Be sure that you can capture the value in the :g_movie_id host variable.
- 12 - normal output will display title and number of rentals
- 13 - exception - there is no movie ID for 13
- 1 - exception - Movie with ID 1 has never been rented
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Version:Current 2013-14 (Click on tutorial image to view snapshot)
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