MySQL 的 CASE WHEN 语句

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/*

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;
           

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