复制代码 代码如下:

/*
 MySQL> select * from sales;
 +-----+------------+--------+--------+--------+------+------------+
 | num | name       | winter | spring | summer | fall | category   |
 +-----+------------+--------+--------+--------+------+------------+
 |   1 | Java       |   1067 |    200 |    150 |  267 | Holiday    |
 |   2 | C          |    970 |    770 |    531 |  486 | Profession |
 |   3 | JavaScript |     53 |     13 |     21 |  856 | Literary   |
 |   4 | SQL        |    782 |    357 |    168 |  250 | Profession |
 |   5 | Oracle     |    589 |    795 |    367 |  284 | Holiday    |
 |   6 | MySQL      |    953 |    582 |    336 |  489 | Literary   |
 |   7 | Cplus      |    752 |    657 |    259 |  478 | Literary   |
 |   8 | Python     |     67 |     23 |     83 |  543 | Holiday    |
 |   9 | PHP        |    673 |     48 |    625 |   52 | Profession |
 +-----+------------+--------+--------+--------+------+------------+
 9 rows in set (0.01 sec)
 mysql> SELECT name AS Name,
     -> CASE category
     -> WHEN "Holiday" THEN "Seasonal"
     -> WHEN "Profession" THEN "Bi_annual"
     -> WHEN "Literary" THEN "Random" END AS "Pattern"
     -> FROM sales;
 +------------+-----------+
 | Name       | Pattern   |
 +------------+-----------+
 | Java       | Seasonal  |
 | C          | Bi_annual |
 | JavaScript | Random    |
 | SQL        | Bi_annual |
 | Oracle     | Seasonal  |
 | MySQL      | Random    |
 | Cplus      | Random    |
 | Python     | Seasonal  |
 | PHP        | Bi_annual |
 +------------+-----------+
 9 rows in set (0.00 sec)
 */
 Drop table sales;
 CREATE TABLE sales(
     num MEDIUMINT NOT NULL AUTO_INCREMENT,
     name CHAR(20),
     winter INT,
     spring INT,
     summer INT,
     fall INT,
     category CHAR(13),
     primary key(num)
 )type=MyISAM;
 insert into sales value(1, 'Java', 1067 , 200, 150, 267,'Holiday');
 insert into sales value(2, 'C',970,770,531,486,'Profession');
 insert into sales value(3, 'JavaScript',53,13,21,856,'Literary');
 insert into sales value(4, 'SQL',782,357,168,250,'Profession');
 insert into sales value(5, 'Oracle',589,795,367,284,'Holiday');
 insert into sales value(6, 'MySQL',953,582,336,489,'Literary');
 insert into sales value(7, 'Cplus',752,657,259,478,'Literary');
 insert into sales value(8, 'Python',67,23,83,543,'Holiday');
 insert into sales value(9, 'PHP',673,48,625,52,'Profession');
 select * from sales;
 SELECT name AS Name,
 CASE category
 WHEN "Holiday" THEN "Seasonal"
 WHEN "Profession" THEN "Bi_annual"
 WHEN "Literary" THEN "Random" END AS "Pattern"
 FROM sales;

复制代码 代码如下:

SELECT CASE WHEN 10*2=30 THEN '30 correct'
WHEN 10*2=40 THEN '40 correct'
ELSE 'Should be 10*2=20'
END;

复制代码 代码如下:

SELECT CASE 10*2
WHEN 20 THEN '20 correct'
WHEN 30 THEN '30 correct'
WHEN 40 THEN '40 correct'
END;

复制代码 代码如下: