最新下载
热门教程
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
mysql when case 条件判断语名用法
时间:2011-10-26 编辑:简简单单 来源:一聚教程网
语法
代码如下 | 复制代码 |
CASE value WHEN [compare-value] THEN result [WHEN [compare-value] THEN result ...] [ELSE result] END CASE WHEN [condition] THEN result [WHEN [condition] THEN result ...] [ELSE result] END |
实例
代码如下 | 复制代码 |
SELECT CASE WHEN 10*2=30 THEN '30 correct' |
复杂点
代码如下 | 复制代码 |
SELECT CASE 10*2 WHEN 20 THEN '20 correct' WHEN 30 THEN '30 correct' WHEN 40 THEN '40 correct' END; |
实例
代码如下 | 复制代码 |
/* mysql> SELECT Name, RatingID AS Rating, -> CASE RatingID -> WHEN 'R' THEN 'Under 17 requires an adult.' -> WHEN 'X' THEN 'No one 17 and under.' -> WHEN 'NR' THEN 'Use discretion when renting.' -> ELSE 'OK to rent to minors.' -> END AS Policy -> FROM DVDs -> ORDER BY Name; +-----------+--------+------------------------------+ | Name | Rating | Policy | +-----------+--------+------------------------------+ | Africa | PG | OK to rent to minors. | | Amadeus | PG | OK to rent to minors. | | Christmas | NR | Use discretion when renting. | | Doc | G | OK to rent to minors. | | Falcon | NR | Use discretion when renting. | | Mash | R | Under 17 requires an adult. | | Show | NR | Use discretion when renting. | | View | NR | Use discretion when renting. | +-----------+--------+------------------------------+ 8 rows in set (0.01 sec) */ Drop table DVDs; CREATE TABLE DVDs ( ID SMALLINT NOT NULL AUTO_INCREMENT PRIMARY KEY, Name VARCHAR(60) NOT NULL, NumDisks TINYINT NOT NULL DEFAULT 1, RatingID VARCHAR(4) NOT NULL, StatID CHAR(3) NOT NULL ) ENGINE=INNODB; INSERT INTO DVDs (Name, NumDisks, RatingID, StatID) VALUES ('Christmas', 1, 'NR', 's1'), ('Doc', 1, 'G', 's2'), ('Africa', 1, 'PG', 's1'), ('Falcon', 1, 'NR', 's2'), ('Amadeus', 1, 'PG', 's2'), ('Show', 2, 'NR', 's2'), ('View', 1, 'NR', 's1'), ('Mash', 2, 'R', 's2'); SELECT Name, RatingID AS Rating, CASE RatingID WHEN 'R' THEN 'Under 17 requires an adult.' WHEN 'X' THEN 'No one 17 and under.' WHEN 'NR' THEN 'Use discretion when renting.' ELSE 'OK to rent to minors.' END AS Policy FROM DVDs ORDER BY Name; |
相关文章
- mysql下mysqladmin日常管理命令总结(必看篇) 07-25
- 查看当前mysql使用频繁的sql语句(详解) 07-11
- 对MySql经常使用语句的全面总结(必看篇) 07-11
- 关于mysql init_connect的几个要点总结 07-10
- MySQL外键约束的禁用与启用命令 07-06
- Python使用pymysql小技巧 06-07