MySQL的单表查询
单表查询
单表查询语法：
select distinct 字段1,字段2... from 表名 where 条件 group by field having筛选 order by
关键字执行的优先级：
- 1.找到表:from
- 2.拿着where指定的约束条件，去文件/表中取出一条条记录
- 3.将取出的一条条记录进行分组group by，如果没有group by，则整体作为一组
- 4.执行select（去重）
- 5.将分组的结果进行having过滤
- 6.将结果按条件排序：order by
- 7.限制结果的显示条数
简单查询：
company.employee
员工id id int
姓名 emp_name varchar
性别 sex enum
年龄 age int
入职日期 hire_date date
岗位 post varchar
职位描述 post_comment varchar
薪水 salary double
办公室 office int
部门编号 depart_id int
# 创建表 create table employee( id int not null unique auto_increment, emp_name varchar(20) not null, sex enum('male','female') not null default 'male', age int(3) unsigned not null default 28, hire_date date not null, post varchar(50), post_comment varchar(100), salary double(15,2), office int, depart_id int ); # 查看表结构 mysql> desc employee; +--------------+-----------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +--------------+-----------------------+------+-----+---------+----------------+ | id | int(11) | NO | PRI | NULL | auto_increment | | emp_name | varchar(20) | NO | | NULL | | | sex | enum('male','female') | NO | | male | | | age | int(3) unsigned | NO | | 28 | | | hire_date | date | NO | | NULL | | | post | varchar(50) | YES | | NULL | | | post_comment | varchar(100) | YES | | NULL | | | salary | double(15,2) | YES | | NULL | | | office | int(11) | YES | | NULL | | | depart_id | int(11) | YES | | NULL | | +--------------+-----------------------+------+-----+---------+----------------+ 10 rows in set (0.09 sec) #插入记录 #三个部门：教学，销售，运营 insert into employee(emp_name,sex,age,hire_date,post,salary,office,depart_id) values ('彭哈哈','male',18,'20170301','教学',7300.33,401,1), ('赵晓明','male',78,'20150302','教学',1000000.31,401,1), ('爱祖国','male',81,'20130305','教学',8300,401,1), ('延阻聚','male',73,'20140701','教学',3500,401,1), ('陈继承','male',28,'20121101','教学',2100,401,1), ('李小荷','female',18,'20110211','教学',9000,401,1), ('赵晓明','male',18,'19000301','教学',30000,401,1), ('高富帅','male',48,'20101111','教学',10000,401,1), ('菟丝子','female',48,'20150311','销售',3000.13,402,2), ('张晓敏','female',38,'20101101','销售',2000.35,402,2), ('冯小刚','female',18,'20110312','销售',1000.37,402,2), ('老小月','female',18,'20160513','销售',3000.29,402,2), ('格格','female',28,'20170127','销售',4000.33,402,2), ('彭消息','male',28,'20160311','运营',10000.13,403,3), ('张国','male',18,'19970312','运营',20000,403,3), ('小路小','female',18,'20130311','运营',19000,403,3), ('罗超','male',18,'20150411','运营',18000,403,3), ('张罗好','female',18,'20140512','运营',17000,403,3);
只查看某张表指定的字段：
select 字段1,字段2,字段3,字段n from 表名；
mysql> select id, emp_name, sex, age from employee; #查看员工姓名性别年龄 +----+-----------+--------+-----+ | id | emp_name | sex | age | +----+-----------+--------+-----+ | 19 | 彭哈哈 | male | 18 | | 20 | 彭哈哈 | male | 18 | | 21 | 赵晓明 | male | 78 | | 22 | 爱祖国 | male | 81 | | 23 | 延阻聚 | male | 73 | | 24 | 陈继承 | male | 28 | | 25 | 李小荷 | female | 18 | | 26 | 赵晓明 | male | 18 | | 27 | 高富帅 | male | 48 | | 28 | 菟丝子 | female | 48 | | 29 | 张晓敏 | female | 38 | | 30 | 冯小刚 | female | 18 | | 31 | 老小月 | female | 18 | | 32 | 格格 | female | 28 | | 33 | 彭消息 | male | 28 | | 34 | 张国 | male | 18 | | 35 | 小路小 | female | 18 | | 36 | 罗超 | male | 18 | | 37 | 张罗好 | female | 18 | +----+-----------+--------+-----+ 19 rows in set (0.00 sec)
查看整张表：
select * from 表名;
mysql> select * from employee; # 查看整张表 +----+-----------+--------+-----+------------+--------+--------------+------------+--------+-----------+ | id | emp_name | sex | age | hire_date | post | post_comment | salary | office | depart_id | +----+-----------+--------+-----+------------+--------+--------------+------------+--------+-----------+ | 19 | 彭哈哈 | male | 18 | 2017-03-01 | 教学 | NULL | 7300.33 | 401 | 1 | | 20 | 彭哈哈 | male | 18 | 2017-03-01 | 教学 | NULL | 7300.33 | 401 | 1 | | 21 | 赵晓明 | male | 78 | 2015-03-02 | 教学 | NULL | 1000000.31 | 401 | 1 | | 22 | 爱祖国 | male | 81 | 2013-03-05 | 教学 | NULL | 8300.00 | 401 | 1 | | 23 | 延阻聚 | male | 73 | 2014-07-01 | 教学 | NULL | 3500.00 | 401 | 1 | | 24 | 陈继承 | male | 28 | 2012-11-01 | 教学 | NULL | 2100.00 | 401 | 1 | | 25 | 李小荷 | female | 18 | 2011-02-11 | 教学 | NULL | 9000.00 | 401 | 1 | | 26 | 赵晓明 | male | 18 | 1900-03-01 | 教学 | NULL | 30000.00 | 401 | 1 | | 27 | 高富帅 | male | 48 | 2010-11-11 | 教学 | NULL | 10000.00 | 401 | 1 | | 28 | 菟丝子 | female | 48 | 2015-03-11 | 销售 | NULL | 3000.13 | 402 | 2 | | 29 | 张晓敏 | female | 38 | 2010-11-01 | 销售 | NULL | 2000.35 | 402 | 2 | | 30 | 冯小刚 | female | 18 | 2011-03-12 | 销售 | NULL | 1000.37 | 402 | 2 | | 31 | 老小月 | female | 18 | 2016-05-13 | 销售 | NULL | 3000.29 | 402 | 2 | | 32 | 格格 | female | 28 | 2017-01-27 | 销售 | NULL | 4000.33 | 402 | 2 | | 33 | 彭消息 | male | 28 | 2016-03-11 | 运营 | NULL | 10000.13 | 403 | 3 | | 34 | 张国 | male | 18 | 1997-03-12 | 运营 | NULL | 20000.00 | 403 | 3 | | 35 | 小路小 | female | 18 | 2013-03-11 | 运营 | NULL | 19000.00 | 403 | 3 | | 36 | 罗超 | male | 18 | 2015-04-11 | 运营 | NULL | 18000.00 | 403 | 3 | | 37 | 张罗好 | female | 18 | 2014-05-12 | 运营 | NULL | 17000.00 | 403 | 3 | +----+-----------+--------+-----+------------+--------+--------------+------------+--------+-----------+ 19 rows in set (0.00 sec)
避免重复distinct：
select distinct post from 表名;
去重功能将重复的去掉只留一个显示
mysql> select distinct post from employee; #查看部门 +--------+ | post | +--------+ | 教学 | | 销售 | | 运营 | +--------+
四则运算查询：
需求：查看所有员工的年薪，薪资乘于12就等于年薪
mysql> select emp_name, salary * 12 FROM employee; #工资乘于12 +-----------+-------------+ | emp_name | salary * 12 | +-----------+-------------+ | 彭哈哈 | 87603.96 | | 彭哈哈 | 87603.96 | | 赵晓明 | 12000003.72 | | 爱祖国 | 99600.00 | | 延阻聚 | 42000.00 | | 陈继承 | 25200.00 | | 李小荷 | 108000.00 | | 赵晓明 | 360000.00 | | 高富帅 | 120000.00 | | 菟丝子 | 36001.56 | | 张晓敏 | 24004.20 | | 冯小刚 | 12004.44 | | 老小月 | 36003.48 | | 格格 | 48003.96 | | 彭消息 | 120001.56 | | 张国 | 240000.00 | | 小路小 | 228000.00 | | 罗超 | 216000.00 | | 张罗好 | 204000.00 | +-----------+-------------+ 19 rows in set (0.00 sec)
需求：查看所有员工的年薪，薪资乘于12就等于年薪并且把字段salary改成Annual_salary
mysql> SELECT emp_name, salary*12 AS Annual_salary FROM employee; +-----------+---------------+ | emp_name | Annual_salary | +-----------+---------------+ | 彭哈哈 | 87603.96 | | 彭哈哈 | 87603.96 | | 赵晓明 | 12000003.72 | | 爱祖国 | 99600.00 | | 延阻聚 | 42000.00 | | 陈继承 | 25200.00 | | 李小荷 | 108000.00 | | 赵晓明 | 360000.00 | | 高富帅 | 120000.00 | | 菟丝子 | 36001.56 | | 张晓敏 | 24004.20 | | 冯小刚 | 12004.44 | | 老小月 | 36003.48 | | 格格 | 48003.96 | | 彭消息 | 120001.56 | | 张国 | 240000.00 | | 小路小 | 228000.00 | | 罗超 | 216000.00 | | 张罗好 | 204000.00 | +-----------+---------------+ 19 rows in set (0.06 sec)
定义格式显示：
concat()函数用于连接字符串
select concat('字符串1',字段,'字符串',字段) from 表名;
mysql> select concat('姓名：',emp_name,'年薪',salary*12) from employee; +-------------------------------------------------+ | concat('姓名：',emp_name,'年薪',salary*12) | +-------------------------------------------------+ | 姓名：彭哈哈年薪87603.96 | | 姓名：彭哈哈年薪87603.96 | | 姓名：赵晓明年薪12000003.72 | | 姓名：爱祖国年薪99600.00 | | 姓名：延阻聚年薪42000.00 | | 姓名：陈继承年薪25200.00 | | 姓名：李小荷年薪108000.00 | | 姓名：赵晓明年薪360000.00 | | 姓名：高富帅年薪120000.00 | | 姓名：菟丝子年薪36001.56 | | 姓名：张晓敏年薪24004.20 | | 姓名：冯小刚年薪12004.44 | | 姓名：老小月年薪36003.48 | | 姓名：格格年薪48003.96 | | 姓名：彭消息年薪120001.56 | | 姓名：张国年薪240000.00 | | 姓名：小路小年薪228000.00 | | 姓名：罗超年薪216000.00 | | 姓名：张罗好年薪204000.00 | +-------------------------------------------------+ 19 rows in set (0.02 sec)
concat_ws()第一个参数为分隔符
需求：查看每个员工的年薪，格式为：姓名：年薪
mysql> select concat_ws(':', emp_name, salary * 12) AS Annual_salary from employee; #第一个数为分隔符 +-----------------------+ | Annual_salary | +-----------------------+ | 彭哈哈:87603.96 | | 彭哈哈:87603.96 | | 赵晓明:12000003.72 | | 爱祖国:99600.00 | | 延阻聚:42000.00 | | 陈继承:25200.00 | | 李小荷:108000.00 | | 赵晓明:360000.00 | | 高富帅:120000.00 | | 菟丝子:36001.56 | | 张晓敏:24004.20 | | 冯小刚:12004.44 | | 老小月:36003.48 | | 格格:48003.96 | | 彭消息:120001.56 | | 张国:240000.00 | | 小路小:228000.00 | | 罗超:216000.00 | | 张罗好:204000.00 | +-----------------------+ 19 rows in set (0.00 sec)
where约束：
where字句中可以使用：
- 1. 比较运算符：> < >= <= <> !=
- 2. between 80 and 100 值在80到100之间
- 3. in(80,90,100) 值是80或90或100
- 4. like 'e%'
- 通配符可以是%或_，
- %表示任意多字符
- _表示一个字符
- 5. 逻辑运算符：在多个条件直接可以使用逻辑运算符 and or not #与或非
条件查询：
select 字段 from 表名
where 字段 = ...;
需求：查询员工表工资等于20000的
select emp_name , salary from employee where salary = 20000;
mysql> select emp_name , salary from employee where salary = 20000; +----------+----------+ | emp_name | salary | +----------+----------+ | 张国 | 20000.00 | +----------+----------+ 1 row in set (0.00 sec)
多条件查询：
需求：查询教学部工资大于10000的
SELECT emp_name,salary FROM employee
WHERE post='teacher' AND salary>10000;
mysql> SELECT emp_name,salary FROM employee -> WHERE post='教学' AND salary>10000; +-----------+------------+ | emp_name | salary | +-----------+------------+ | 赵晓明 | 1000000.31 | | 赵晓明 | 30000.00 | +-----------+------------+ 2 rows in set (0.00 sec)
关键字between and查询：
需求：查询员工薪资15000至20000的人
ysql> select emp_name,salary from employee -> where salary between 15000 and 20000; +-----------+----------+ | emp_name | salary | +-----------+----------+ | 张国 | 20000.00 | | 小路小 | 19000.00 | | 罗超 | 18000.00 | | 张罗好 | 17000.00 | +-----------+----------+ 4 rows in set (0.00 sec)
关键字is null(判断某个字段是否为null不能用=号，需要用is)
mysql>SELECT emp_name,post_comment FROM employee -> WHERE post_comment IS NULL; +-----------+--------------+ | emp_name | post_comment | +-----------+--------------+ | 彭哈哈 | NULL | | 彭哈哈 | NULL | | 赵晓明 | NULL | | 爱祖国 | NULL | | 延阻聚 | NULL | | 陈继承 | NULL | | 李小荷 | NULL | | 赵晓明 | NULL | | 高富帅 | NULL | | 菟丝子 | NULL | | 张晓敏 | NULL | | 冯小刚 | NULL | | 老小月 | NULL | | 格格 | NULL | | 彭消息 | NULL | | 张国 | NULL | | 小路小 | NULL | | 罗超 | NULL | | 张罗好 | NULL | +-----------+--------------+ 19 rows in set (0.00 sec)
关键字in集合查询：
#查询工资为3000或3500，4000或9000 mysql>SELECT emp_name,salary FROM employee ->WHERE salary=3000 OR salary=3500 OR salary=4000 OR salary=9000; +-----------+---------+ | emp_name | salary | +-----------+---------+ | 延阻聚 | 3500.00 | | 李小荷 | 9000.00 | +-----------+---------+ 2 rows in set (0.00 sec) mysql>SELECT emp_name,salary FROM employee ->WHERE salary IN (3000,3500,4000,9000) ; +-----------+---------+ | emp_name | salary | +-----------+---------+ | 延阻聚 | 3500.00 | | 李小荷 | 9000.00 | +-----------+---------+ 2 rows in set (0.03 sec) mysql> SELECT emp_name,salary FROM employee -> WHERE salary NOT IN (3000,3500,4000,9000) ; #not不寻找某某或。。。 +-----------+------------+ | emp_name | salary | +-----------+------------+ | 彭哈哈 | 7300.33 | | 彭哈哈 | 7300.33 | | 赵晓明 | 1000000.31 | | 爱祖国 | 8300.00 | | 陈继承 | 2100.00 | | 赵晓明 | 30000.00 | | 高富帅 | 10000.00 | | 菟丝子 | 3000.13 | | 张晓敏 | 2000.35 | | 冯小刚 | 1000.37 | | 老小月 | 3000.29 | | 格格 | 4000.33 | | 彭消息 | 10000.13 | | 张国 | 20000.00 | | 小路小 | 19000.00 | | 罗超 | 18000.00 | | 张罗好 | 17000.00 | +-----------+------------+ 17 rows in set (0.00 sec)
关键字like模糊查询：
通配符'%'表示任意长度的任意内容
mysql>SELECT * FROM employee ->WHERE emp_name LIKE '张%'; #以张开头后面不限都能查询出来 +----+-----------+--------+-----+------------+--------+--------------+----------+--------+-----------+ | id | emp_name | sex | age | hire_date | post | post_comment | salary | office | depart_id | +----+-----------+--------+-----+------------+--------+--------------+----------+--------+-----------+ | 29 | 张晓敏 | female | 38 | 2010-11-01 | 销售 | NULL | 2000.35 | 402 | 2 | | 34 | 张国 | male | 18 | 1997-03-12 | 运营 | NULL | 20000.00 | 403 | 3 | | 37 | 张罗好 | female | 18 | 2014-05-12 | 运营 | NULL | 17000.00 | 403 | 3 | +----+-----------+--------+-----+------------+--------+--------------+----------+--------+-----------+ 3 rows in set (0.00 sec)
通配符：'_'一个字符长度的任意内容
mysql> SELECT * FROM employee -> WHERE emp_name LIKE '赵__'; +----+-----------+------+-----+------------+--------+--------------+------------+--------+-----------+ | id | emp_name | sex | age | hire_date | post | post_comment | salary | office | depart_id | +----+-----------+------+-----+------------+--------+--------------+------------+--------+-----------+ | 21 | 赵晓明 | male | 78 | 2015-03-02 | 教学 | NULL | 1000000.31 | 401 | 1 | | 26 | 赵晓明 | male | 18 | 1900-03-01 | 教学 | NULL | 30000.00 | 401 | 1 | +----+-----------+------+-----+------------+--------+--------------+------------+--------+-----------+ 2 rows in set (0.05 sec)
聚合函数：聚合函数聚合的是组的内容，若是没有分组，则默认一组
- count 求个数
- max 求最大值
- min 求最小值
- sum 求和
- avg 求平均
mysql> select count( * ) from employee; #求雇员表的个数 +------------+ | count( * ) | +------------+ | 19 | +------------+ 1 row in set (0.00 sec) mysql> select max(salary) from employee; #求雇员表里的薪资最大值 +-------------+ | max(salary) | +-------------+ | 1000000.31 | +-------------+ 1 row in set (0.00 sec) mysql> select min(salary) from employee; #求雇员表里的薪资最大值 +-------------+ | min(salary) | +-------------+ | 1000.37 | +-------------+ 1 row in set (0.00 sec) mysql> select sum(salary) from employee; #求雇员表的和 +-------------+ | sum(salary) | +-------------+ | 1174502.57 | +-------------+ 1 row in set (0.00 sec) mysql> select avg(salary) from employee; #求雇员表的平均值 +--------------+ | avg(salary) | +--------------+ | 61815.924737 | +--------------+ 1 row in set (0.00 sec)
having：过滤语句
#！！！执行优先级从高到低：where > group by > having #1. Where 发生在分组group by之前，因而Where中可以有任意字段，但是绝对不能使用聚合函数。 #2. Having发生在分组group by之后，因而Having中可以使用分组的字段，无法直接取到其他字段,可以使用聚合函数
- 在having条件中可以使用聚合函数,在where中不行
- 适合去筛选符合条件的某一组数据,而不是某一行数据
- 先分组再过滤 : 求平均薪资大于xx的部门,求人数大于xx的性别,求大于xx人的年龄段
- 查询各岗位内包含的员工个数小于2的岗位名、岗位内包含员工名字、个数
- group by post having count(id) < 2;
排序： order by
- 默认是升序 asc
- 降序 desc
- select * from employee order by age, salary desc;
- 优先根据age从小到大排,在age相同的情况下,再根据薪资从大到小排
#升序排序 mysql> select * from employee order by salary; +----+-----------+--------+-----+------------+--------+--------------+------------+--------+-----------+ | id | emp_name | sex | age | hire_date | post | post_comment | salary | office | depart_id | +----+-----------+--------+-----+------------+--------+--------------+------------+--------+-----------+ | 30 | 冯小刚 | female | 18 | 2011-03-12 | 销售 | NULL | 1000.37 | 402 | 2 | | 29 | 张晓敏 | female | 38 | 2010-11-01 | 销售 | NULL | 2000.35 | 402 | 2 | | 24 | 陈继承 | male | 28 | 2012-11-01 | 教学 | NULL | 2100.00 | 401 | 1 | | 28 | 菟丝子 | female | 48 | 2015-03-11 | 销售 | NULL | 3000.13 | 402 | 2 | | 31 | 老小月 | female | 18 | 2016-05-13 | 销售 | NULL | 3000.29 | 402 | 2 | | 23 | 延阻聚 | male | 73 | 2014-07-01 | 教学 | NULL | 3500.00 | 401 | 1 | | 32 | 格格 | female | 28 | 2017-01-27 | 销售 | NULL | 4000.33 | 402 | 2 | | 19 | 彭哈哈 | male | 18 | 2017-03-01 | 教学 | NULL | 7300.33 | 401 | 1 | | 20 | 彭哈哈 | male | 18 | 2017-03-01 | 教学 | NULL | 7300.33 | 401 | 1 | | 22 | 爱祖国 | male | 81 | 2013-03-05 | 教学 | NULL | 8300.00 | 401 | 1 | | 25 | 李小荷 | female | 18 | 2011-02-11 | 教学 | NULL | 9000.00 | 401 | 1 | | 27 | 高富帅 | male | 48 | 2010-11-11 | 教学 | NULL | 10000.00 | 401 | 1 | | 33 | 彭消息 | male | 28 | 2016-03-11 | 运营 | NULL | 10000.13 | 403 | 3 | | 37 | 张罗好 | female | 18 | 2014-05-12 | 运营 | NULL | 17000.00 | 403 | 3 | | 36 | 罗超 | male | 18 | 2015-04-11 | 运营 | NULL | 18000.00 | 403 | 3 | | 35 | 小路小 | female | 18 | 2013-03-11 | 运营 | NULL | 19000.00 | 403 | 3 | | 34 | 张国 | male | 18 | 1997-03-12 | 运营 | NULL | 20000.00 | 403 | 3 | | 26 | 赵晓明 | male | 18 | 1900-03-01 | 教学 | NULL | 30000.00 | 401 | 1 | | 21 | 赵晓明 | male | 78 | 2015-03-02 | 教学 | NULL | 1000000.31 | 401 | 1 | +----+-----------+--------+-----+------------+--------+--------------+------------+--------+-----------+ 19 rows in set (0.00 sec) #倒序排序 mysql> select * from employee order by salary asc; +----+-----------+--------+-----+------------+--------+--------------+------------+--------+-----------+ | id | emp_name | sex | age | hire_date | post | post_comment | salary | office | depart_id | +----+-----------+--------+-----+------------+--------+--------------+------------+--------+-----------+ | 30 | 冯小刚 | female | 18 | 2011-03-12 | 销售 | NULL | 1000.37 | 402 | 2 | | 29 | 张晓敏 | female | 38 | 2010-11-01 | 销售 | NULL | 2000.35 | 402 | 2 | | 24 | 陈继承 | male | 28 | 2012-11-01 | 教学 | NULL | 2100.00 | 401 | 1 | | 28 | 菟丝子 | female | 48 | 2015-03-11 | 销售 | NULL | 3000.13 | 402 | 2 | | 31 | 老小月 | female | 18 | 2016-05-13 | 销售 | NULL | 3000.29 | 402 | 2 | | 23 | 延阻聚 | male | 73 | 2014-07-01 | 教学 | NULL | 3500.00 | 401 | 1 | | 32 | 格格 | female | 28 | 2017-01-27 | 销售 | NULL | 4000.33 | 402 | 2 | | 19 | 彭哈哈 | male | 18 | 2017-03-01 | 教学 | NULL | 7300.33 | 401 | 1 | | 20 | 彭哈哈 | male | 18 | 2017-03-01 | 教学 | NULL | 7300.33 | 401 | 1 | | 22 | 爱祖国 | male | 81 | 2013-03-05 | 教学 | NULL | 8300.00 | 401 | 1 | | 25 | 李小荷 | female | 18 | 2011-02-11 | 教学 | NULL | 9000.00 | 401 | 1 | | 27 | 高富帅 | male | 48 | 2010-11-11 | 教学 | NULL | 10000.00 | 401 | 1 | | 33 | 彭消息 | male | 28 | 2016-03-11 | 运营 | NULL | 10000.13 | 403 | 3 | | 37 | 张罗好 | female | 18 | 2014-05-12 | 运营 | NULL | 17000.00 | 403 | 3 | | 36 | 罗超 | male | 18 | 2015-04-11 | 运营 | NULL | 18000.00 | 403 | 3 | | 35 | 小路小 | female | 18 | 2013-03-11 | 运营 | NULL | 19000.00 | 403 | 3 | | 34 | 张国 | male | 18 | 1997-03-12 | 运营 | NULL | 20000.00 | 403 | 3 | | 26 | 赵晓明 | male | 18 | 1900-03-01 | 教学 | NULL | 30000.00 | 401 | 1 | | 21 | 赵晓明 | male | 78 | 2015-03-02 | 教学 | NULL | 1000000.31 | 401 | 1 | +----+-----------+--------+-----+------------+--------+--------------+------------+--------+-----------+ 19 rows in set (0.00 sec) # 优先根据age从小到大排,在age相同的情况下,再根据薪资从大到小排 mysql> select * from employee order by age, salary desc; +----+-----------+--------+-----+------------+--------+--------------+------------+--------+-----------+ | id | emp_name | sex | age | hire_date | post | post_comment | salary | office | depart_id | +----+-----------+--------+-----+------------+--------+--------------+------------+--------+-----------+ | 26 | 赵晓明 | male | 18 | 1900-03-01 | 教学 | NULL | 30000.00 | 401 | 1 | | 34 | 张国 | male | 18 | 1997-03-12 | 运营 | NULL | 20000.00 | 403 | 3 | | 35 | 小路小 | female | 18 | 2013-03-11 | 运营 | NULL | 19000.00 | 403 | 3 | | 36 | 罗超 | male | 18 | 2015-04-11 | 运营 | NULL | 18000.00 | 403 | 3 | | 37 | 张罗好 | female | 18 | 2014-05-12 | 运营 | NULL | 17000.00 | 403 | 3 | | 25 | 李小荷 | female | 18 | 2011-02-11 | 教学 | NULL | 9000.00 | 401 | 1 | | 19 | 彭哈哈 | male | 18 | 2017-03-01 | 教学 | NULL | 7300.33 | 401 | 1 | | 20 | 彭哈哈 | male | 18 | 2017-03-01 | 教学 | NULL | 7300.33 | 401 | 1 | | 31 | 老小月 | female | 18 | 2016-05-13 | 销售 | NULL | 3000.29 | 402 | 2 | | 30 | 冯小刚 | female | 18 | 2011-03-12 | 销售 | NULL | 1000.37 | 402 | 2 | | 33 | 彭消息 | male | 28 | 2016-03-11 | 运营 | NULL | 10000.13 | 403 | 3 | | 32 | 格格 | female | 28 | 2017-01-27 | 销售 | NULL | 4000.33 | 402 | 2 | | 24 | 陈继承 | male | 28 | 2012-11-01 | 教学 | NULL | 2100.00 | 401 | 1 | | 29 | 张晓敏 | female | 38 | 2010-11-01 | 销售 | NULL | 2000.35 | 402 | 2 | | 27 | 高富帅 | male | 48 | 2010-11-11 | 教学 | NULL | 10000.00 | 401 | 1 | | 28 | 菟丝子 | female | 48 | 2015-03-11 | 销售 | NULL | 3000.13 | 402 | 2 | | 23 | 延阻聚 | male | 73 | 2014-07-01 | 教学 | NULL | 3500.00 | 401 | 1 | | 21 | 赵晓明 | male | 78 | 2015-03-02 | 教学 | NULL | 1000000.31 | 401 | 1 | | 22 | 爱祖国 | male | 81 | 2013-03-05 | 教学 | NULL | 8300.00 | 401 | 1 | +----+-----------+--------+-----+------------+--------+--------------+------------+--------+-----------+ 19 rows in set (0.00 sec)
