Mega Code Archive
The expression in the select list subtracts the Reserved value from the total
<![CDATA[
mysql>
mysql>
mysql> CREATE TABLE CDs
-> (
-> CDID SMALLINT NOT NULL AUTO_INCREMENT PRIMARY KEY,
-> CDName VARCHAR(50) NOT NULL,
-> InStock SMALLINT UNSIGNED NOT NULL,
-> OnOrder SMALLINT UNSIGNED NOT NULL,
-> Reserved SMALLINT UNSIGNED NOT NULL,
-> Department ENUM('Classical', 'Popular') NOT NULL,
-> Category VARCHAR(20) NOT NULL,
-> RowUpdate TIMESTAMP NOT NULL
-> );
Query OK, 0 rows affected (0.01 sec)
mysql>
mysql> INSERT INTO CDs (CDName, InStock, OnOrder, Reserved, Department, Category) VALUES
-> ('Xml', 10, 5, 3, 'Popular', 'Rock'),
-> ('Java', 10, 5, 3, 'Classical', 'Opera'),
-> ('SQL', 17, 4, 1, 'Popular', 'Jazz'),
-> ('MySQL', 9, 4, 2, 'Classical', 'Dance'),
-> ('CSS', 24, 2, 5, 'Classical', 'General'),
-> ('HTML', 16, 6, 8, 'Classical', 'Vocal'),
-> ('Oracle', 2, 25, 6, 'Popular', 'Blues'),
-> ('Javascript', 32, 3, 10, 'Popular', 'Jazz'),
-> ('Data type', 12, 15, 13, 'Popular', 'Country'),
-> ('Flash', 5, 20, 10, 'Popular', 'New Age'),
-> ('Ajax', 24, 11, 14, 'Popular', 'New Age'),
-> ('Photoshop', 42, 17, 17, 'Classical', 'General'),
-> ('Word', 25, 44, 28, 'Classical', 'Dance'),
-> ('iPhone', 32, 15, 12, 'Classical', 'General'),
-> ('MacBook', 20, 10, 5, 'Classical', 'Opera'),
-> ('Linux', 23, 12, 8, 'Classical', 'General'),
-> ('Shell', 23, 10, 17, 'Popular', 'Country'),
-> ('Pascal', 18, 20, 10, 'Popular', 'Jazz'),
-> ('Ruby', 22, 5, 7, 'Popular', 'Blues'),
-> ('Sql Server', 28, 17, 16, 'Classical', 'General'),
-> ('Opera', 10, 35, 12, 'Classical', 'Opera'),
-> ('Safari', 15, 30, 14, 'Popular', 'Blues'),
-> ('C', 42, 0, 8, 'Popular', 'Blues'),
-> ('C++', 16, 8, 8, 'Classical', 'General');
Query OK, 24 rows affected (0.00 sec)
Records: 24 Duplicates: 0 Warnings: 0
mysql>
mysql>
mysql> SELECT CDName, InStock+OnOrder-Reserved AS Total
-> FROM CDs;
+------------+-------+
| CDName | Total |
+------------+-------+
| Xml | 12 |
| Java | 12 |
| SQL | 20 |
| MySQL | 11 |
| CSS | 21 |
| HTML | 14 |
| Oracle | 21 |
| Javascript | 25 |
| Data type | 14 |
| Flash | 15 |
| Ajax | 21 |
| Photoshop | 42 |
| Word | 41 |
| iPhone | 35 |
| MacBook | 25 |
| Linux | 27 |
| Shell | 16 |
| Pascal | 28 |
| Ruby | 20 |
| Sql Server | 29 |
| Opera | 33 |
| Safari | 31 |
| C | 34 |
| C++ | 16 |
+------------+-------+
24 rows in set (0.00 sec)
mysql>
mysql> drop table CDs;
Query OK, 0 rows affected (0.00 sec)
mysql>
]]>