Mysql case when 用法

随便建个表

DROP TABLE IF EXISTS `test`;
CREATE TABLE `test`  (
  `id` int(11) NULL DEFAULT NULL,
  `name` char(5) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,
  `sex` char(1) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL
) ENGINE = MyISAM CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Fixed;

-- ----------------------------

-- Records of test

-- ----------------------------

INSERT INTO `test` VALUES (1, '张三', 'm');
INSERT INTO `test` VALUES (2, '李四', 'f');
INSERT INTO `test` VALUES (3, '王五', 'm');
INSERT INTO `test` VALUES (4, '老刘', 'f');
INSERT INTO `test` VALUES (5, '七人众', 'l');

SELECT
	id,
CASE
WHEN sex='f' THEN'男的'  //当字段sex里面有值为f,则变为男的
when sex='m' then'女的'  
	ELSE '人妖'         //其他的值(不是f也是m),则变为人妖
END '性别'              //结果的字段名称
FROM
	test;