建表语句：
-- 学生表CREATE TABLE student (st_id varchar(64) NOT NULL DEFAULT '' COMMENT '编号',st_name varchar(255) DEFAULT '' COMMENT '姓名',st_age int(3) DEFAULT NULL COMMENT '年龄',st_address varchar(255) DEFAULT NULL COMMENT '地址',st_sex varchar(8) DEFAULT NULL COMMENT '性别',st_status int(2) DEFAULT NULL COMMENT '状态, 0-正常， 1-异常. ',create_date datetime DEFAULT NULL COMMENT '创建时间',update_date datetime DEFAULT NULL COMMENT '修改时间',PRIMARY KEY (st_id)) ENGINE=InnoDB DEFAULT CHARSET=utf8 COMMENT='学生表';INSERT INTO student (st_id, st_name, st_age, st_address, st_sex, st_status, create_date, update_date) VALUES ('001', '侯耀华', '77', '北京市-海淀区', '男', NULL, '-06-10 10:56:21', NULL);INSERT INTO student (st_id, st_name, st_age, st_address, st_sex, st_status, create_date, update_date) VALUES ('002', '郭德纲', '45', '河北省-保定市', '男', '0', '-06-09 16:56:21', NULL);INSERT INTO student (st_id, st_name, st_age, st_address, st_sex, st_status, create_date, update_date) VALUES ('003', '曹云金', '33', '河南省-洛阳市', '男', '-5', '-06-10 13:22:21', NULL);INSERT INTO student (st_id, st_name, st_age, st_address, st_sex, st_status, create_date, update_date) VALUES ('004', '岳云鹏', '31', '河南省-周口市', '男', '0', '-06-08 09:35:27', NULL);INSERT INTO student (st_id, st_name, st_age, st_address, st_sex, st_status, create_date, update_date) VALUES ('005', '宋丹丹', '52', '黑龙江-佳木斯', '女', '0', '-06-09 07:35:27', NULL);INSERT INTO student (st_id, st_name, st_age, st_address, st_sex, st_status, create_date, update_date) VALUES ('006', '倪妮', '31', '江苏省-南京市', '女', '-5', '-06-08 04:16:41', NULL);INSERT INTO student (st_id, st_name, st_age, st_address, st_sex, st_status, create_date, update_date) VALUES ('007', '江流儿', '445', '明朝-汴梁人氏', '男', '0', '1798-06-11 15:11:47', NULL);INSERT INTO student (st_id, st_name, st_age, st_address, st_sex, st_status, create_date, update_date) VALUES ('008', '赵丽颖', '31', '河南省-平顶山市', '女', '0', '-06-06 03:24:51', NULL);INSERT INTO student (st_id, st_name, st_age, st_address, st_sex, st_status, create_date, update_date) VALUES ('009', '李云鹤', '33', '河北省-怀柔', '男', '2', NULL, NULL);INSERT INTO student (st_id, st_name, st_age, st_address, st_sex, st_status, create_date, update_date) VALUES ('user_002', '吴玉', '19', '福建省-龙岩市', '女', NULL, '-06-08 10:14:02', NULL);INSERT INTO student (st_id, st_name, st_age, st_address, st_sex, st_status, create_date, update_date) VALUES ('user_003', '上官飞', '20', '河北省-廊坊市', '男', NULL, '-06-07 10:14:06', NULL);
CASE WHEN 函数使用.
SELECTCASE WHEN s.st_age < 35 AND s.st_sex = '男'THEN '青年-男'WHEN s.st_age < 35 AND s.st_sex = '女'THEN '青年-女'WHEN s.st_age < 60 AND s.st_sex = '男'THEN '中年-男'WHEN s.st_age < 60 AND s.st_sex = '女'THEN '中年-女' ELSE NULLEND AS message,s.*FROM student s;
SQL语句运行结果如下所示：
