mysql> create table employee(-> id int primary key auto_increment,-> emp_name char(12) not null,-> sex enum('male','female') not null default 'male', #大部分是男的-> age int(3) unsigned not null default 28,-> hire_date date not null,-> post char(15),-> post_comment varchar(100),-> salary float(15,2),-> office int, #一个部门一个屋子-> depart_id int-> ); mysql> insert into employee(emp_name,sex,age,hire_date,post,salary,office,depart_id) values-> ('egon','male',18,'20170301','老男孩驻沙河办事处外交大使',7300.33,401,1), #以下是教学部-> ('alex','male',78,'20150302','teacher',1000000.31,401,1),-> ('wupeiqi','male',81,'20130305','teacher',8300,401,1),-> ('yuanhao','male',73,'20140701','teacher',3500,401,1),-> ('liwenzhou','male',28,'20121101','teacher',2100,401,1),-> ('jingliyang','female',18,'20110211','teacher',9000,401,1),-> ('jinxin','male',18,'19000301','teacher',30000,401,1),-> ('成龙','male',48,'20101111','teacher',10000,401,1),->-> ('歪歪','female',48,'20150311','sale',3000.13,402,2),#以下是销售部门-> ('丫丫','female',38,'20101101','sale',2000.35,402,2),-> ('丁丁','female',18,'20110312','sale',1000.37,402,2),-> ('星星','female',18,'20160513','sale',3000.29,402,2),-> ('格格','female',28,'20170127','sale',4000.33,402,2),->-> ('张野','male',28,'20160311','operation',10000.13,403,3), #以下是运营部门-> ('程咬金','male',18,'19970312','operation',20000,403,3),-> ('程咬银','female',18,'20130311','operation',19000,403,3),-> ('程咬铜','male',18,'20150411','operation',18000,403,3),-> ('程咬铁','female',18,'20140512','operation',17000,403,3)-> ;
增
insert into 表名 values (数据)
insert into(字段名) 表名 values (数据);
删
delete from 表名 where 条件; 删除符合条件的数据 delete from 表名; 清空表
改
update 表名 set 字段名=值 where 条件;
update 表名 set 字段名1=值1,字段名2=值2 where 条件; 改变符合条件的两个字段的值
查
select关键字
select * from 表名; 查询所有内容 select 字段1,字段2 from 表名; 查找指定列的内容 select distinct 字段名 from 表名; 去重显示 select 字段*12 from 表名; 做四则运算 select 字段 as 新字段名 from 表名; 重命名 没有更改原表的字段,只是在本次查询中显示新的字段名 concat concat_ws 拼接
case 开始一个条件语句 when 条件1 then 字段操作 when 条件2 then 字段操作 else 字段操作 end 结束条件语句
# 去重显示所有的部门 mysql> select distinct post from employee; +-----------------------------------------+ | post | +-----------------------------------------+ | 老男孩驻沙河办事处外交大使 | | teacher | | sale | | operation | +-----------------------------------------+ 4 rows in set (0.00 sec)# 计算出每个人的年薪,并将字段名显示为年薪 mysql> select emp_name,salary*12 as annual_year from employee; +------------+-------------+ | emp_name | annual_year | +------------+-------------+ | egon | 87603.96 | | alex | 12000003.75 | | wupeiqi | 99600.00 | | yuanhao | 42000.00 | | liwenzhou | 25200.00 | | jingliyang | 108000.00 | | jinxin | 360000.00 | | 成龙 | 120000.00 | | 歪歪 | 36001.56 | | 丫丫 | 24004.20 | | 丁丁 | 12004.44 | | 星星 | 36003.48 | | 格格 | 48003.96 | | 张野 | 120001.56 | | 程咬金 | 240000.00 | | 程咬银 | 228000.00 | | 程咬铜 | 216000.00 | | 程咬铁 | 204000.00 | +------------+-------------+ 18 rows in set (0.00 sec)# 按照一定格式拼接显示 mysql> select concat('<姓名:',emp_name,'> <薪资:',salary,'>') from employee; +------------------------------------------------------+ | concat('<姓名:',emp_name,'> <薪资:',salary,'>') | +------------------------------------------------------+ | <姓名:egon> <薪资:7300.33> | | <姓名:alex> <薪资:1000000.31> | | <姓名:wupeiqi> <薪资:8300.00> | | <姓名:yuanhao> <薪资:3500.00> | | <姓名:liwenzhou> <薪资:2100.00> | | <姓名:jingliyang> <薪资:9000.00> | | <姓名:jinxin> <薪资:30000.00> | | <姓名:成龙> <薪资:10000.00> | | <姓名:歪歪> <薪资:3000.13> | | <姓名:丫丫> <薪资:2000.35> | | <姓名:丁丁> <薪资:1000.37> | | <姓名:星星> <薪资:3000.29> | | <姓名:格格> <薪资:4000.33> | | <姓名:张野> <薪资:10000.13> | | <姓名:程咬金> <薪资:20000.00> | | <姓名:程咬银> <薪资:19000.00> | | <姓名:程咬铜> <薪资:18000.00> | | <姓名:程咬铁> <薪资:17000.00> | +------------------------------------------------------+ 18 rows in set (0.00 sec)
where条件
对值的判断 = > < != <> >= <= 对范围的判断 between 小的值 and 大的值 上下包含 is null 判断是不是为空 in (值1,值2,值3,值4) 模糊匹配 like%是通配符,匹配任意长度的任意内容'a%' 查找以a开头的 '%a' 查找以a结尾的'%a%' 查找中间包含a的_ 匹配任意一个长度的内容'_a' 匹配任意一个字符+a'a__' 以a开头,后面是任意两个字符 逻辑运算符 and or not
# 筛选出老师中年龄超过30岁的姓名,年龄,薪资 mysql> select emp_name,age,salary from employee where post='teacher'and age>30;; +----------+-----+------------+ | emp_name | age | salary | +----------+-----+------------+ | alex | 78 | 1000000.31 | | wupeiqi | 81 | 8300.00 | | yuanhao | 73 | 3500.00 | | 成龙 | 48 | 10000.00 | +----------+-----+------------+ 4 rows in set (0.00 sec)# 筛选出老师中薪资在9000到10000之间的姓名,年龄,薪资 mysql> select emp_name,age,salary from employee where post='teacher'and salary between 9000 and 10000; +------------+-----+----------+ | emp_name | age | salary | +------------+-----+----------+ | jingliyang | 18 | 9000.00 | | 成龙 | 48 | 10000.00 | +------------+-----+----------+ 2 rows in set (0.00 sec)# 筛选出工资是10000或者9000或者3000的员工姓名,年龄,薪资 mysql> select emp_name,age,salary from employee where salary in (10000,9000,30000); +------------+-----+----------+ | emp_name | age | salary | +------------+-----+----------+ | jingliyang | 18 | 9000.00 | | jinxin | 18 | 30000.00 | | 成龙 | 48 | 10000.00 | +------------+-----+----------+ 3 rows in set (0.00 sec)# 筛选名字以'jin'开头的姓名和年薪 mysql> select emp_name,salary*12 as annual_salary from employee where emp_name like 'jin%'; +------------+---------------+ | emp_name | annual_salary | +------------+---------------+ | jingliyang | 108000.00 | | jinxin | 360000.00 | +------------+---------------+ 2 rows in set (0.00 sec)
group by 分组
select 字段名 from 表名 where 条件 group by 字段名; #分成几个组 就显示几条数据 需要用到group_concat
# 按照部门分组,统计每个部门人的姓名 mysql> select post,group_concat(emp_name) from employee group by post; +-----------------------------------------+---------------------------------------------------------+ | post | group_concat(emp_name) | +-----------------------------------------+---------------------------------------------------------+ | operation | 程咬铁,程咬铜,程咬银,程咬金,张野 | | sale | 格格,星星,丁丁,丫丫,歪歪 | | teacher | 成龙,jinxin,jingliyang,liwenzhou,yuanhao,wupeiqi,alex | | 老男孩驻沙河办事处外交大使 | egon | +-----------------------------------------+---------------------------------------------------------+ 4 rows in set (0.00 sec)
聚合函数
count() 统计有多少条记录是符合条件的 统计字段内容不能为空,如果为空,不进行累加
min(字段名)
max(字段名)
avg(字段名)
sum(字段名) # 统计出男性和女性的个数 mysql> select sex,count(sex) from employee group by sex; +--------+------------+ | sex | count(sex) | +--------+------------+ | male | 10 | | female | 8 | +--------+------------+ 2 rows in set (0.00 sec)# 计算男性和女性的平均薪资 mysql> select sex,avg(salary) from employee group by sex; +--------+---------------+ | sex | avg(salary) | +--------+---------------+ | male | 110920.077246 | | female | 7250.183746 | +--------+---------------+ 2 rows in set (0.00 sec)
分组 + 聚合函数
聚合函数只是代表一列的结果,并不能直接将这一列相关的一行数据直接取到
#求各部门平均薪资 mysql> select post,avg(salary) from employee group by post; +-----------------------------------------+---------------+ | post | avg(salary) | +-----------------------------------------+---------------+ | operation | 16800.025977 | | sale | 2600.293994 | | teacher | 151842.901786 | | 老男孩驻沙河办事处外交大使 | 7300.330078 | +-----------------------------------------+---------------+ 4 rows in set (0.12 sec)
having 过滤
是根据分组的结果进行过滤的,对一个组的数据进行进一步筛选的时候,使用having关键字,对条件的使用,应该尽量使用where进行单条数据的筛选
# 查询各岗位平均薪资大于10000的岗位名、平均工资 mysql> select post,avg(salary) from employee group by post having avg(salary) > 10000; +-----------+---------------+ | post | avg(salary) | +-----------+---------------+ | operation | 16800.025977 | | teacher | 151842.901786 | +-----------+---------------+ 2 rows in set (0.01 sec)
order by 排序
先根据条件找到所有符合条件的行,对这些行中的某一个字段对这些信息进行排序,默认升序 asc 最后写desc 降序
# 按照年龄升序排列 mysql> select * from employee order by age; +----+------------+--------+-----+------------+-----------------------------------------+--------------+------------+--------+-----------+ | id | emp_name | sex | age | hire_date | post | post_comment | salary | office | depart_id | +----+------------+--------+-----+------------+-----------------------------------------+--------------+------------+--------+-----------+ | 1 | egon | male | 18 | 2017-03-01 | 老男孩驻沙河办事处外交大使 | NULL | 7300.33 | 401 | 1 | | 17 | 程咬铜 | male | 18 | 2015-04-11 | operation | NULL | 18000.00 | 403 | 3 | | 16 | 程咬银 | female | 18 | 2013-03-11 | operation | NULL | 19000.00 | 403 | 3 | | 15 | 程咬金 | male | 18 | 1997-03-12 | operation | NULL | 20000.00 | 403 | 3 | | 12 | 星星 | female | 18 | 2016-05-13 | sale | NULL | 3000.29 | 402 | 2 | | 11 | 丁丁 | female | 18 | 2011-03-12 | sale | NULL | 1000.37 | 402 | 2 | | 18 | 程咬铁 | female | 18 | 2014-05-12 | operation | NULL | 17000.00 | 403 | 3 | | 7 | jinxin | male | 18 | 1900-03-01 | teacher | NULL | 30000.00 | 401 | 1 | | 6 | jingliyang | female | 18 | 2011-02-11 | teacher | NULL | 9000.00 | 401 | 1 | | 13 | 格格 | female | 28 | 2017-01-27 | sale | NULL | 4000.33 | 402 | 2 | | 14 | 张野 | male | 28 | 2016-03-11 | operation | NULL | 10000.13 | 403 | 3 | | 5 | liwenzhou | male | 28 | 2012-11-01 | teacher | NULL | 2100.00 | 401 | 1 | | 10 | 丫丫 | female | 38 | 2010-11-01 | sale | NULL | 2000.35 | 402 | 2 | | 9 | 歪歪 | female | 48 | 2015-03-11 | sale | NULL | 3000.13 | 402 | 2 | | 8 | 成龙 | male | 48 | 2010-11-11 | teacher | NULL | 10000.00 | 401 | 1 | | 4 | yuanhao | male | 73 | 2014-07-01 | teacher | NULL | 3500.00 | 401 | 1 | | 2 | alex | male | 78 | 2015-03-02 | teacher | NULL | 1000000.31 | 401 | 1 | | 3 | wupeiqi | male | 81 | 2013-03-05 | teacher | NULL | 8300.00 | 401 | 1 | +----+------------+--------+-----+------------+-----------------------------------------+--------------+------------+--------+-----------+ 18 rows in set (0.00 sec)# 按照薪资降序排列 mysql> select * from employee order by salary desc; +----+------------+--------+-----+------------+-----------------------------------------+--------------+------------+--------+-----------+ | id | emp_name | sex | age | hire_date | post | post_comment | salary | office | depart_id | +----+------------+--------+-----+------------+-----------------------------------------+--------------+------------+--------+-----------+ | 2 | alex | male | 78 | 2015-03-02 | teacher | NULL | 1000000.31 | 401 | 1 | | 7 | jinxin | male | 18 | 1900-03-01 | teacher | NULL | 30000.00 | 401 | 1 | | 15 | 程咬金 | male | 18 | 1997-03-12 | operation | NULL | 20000.00 | 403 | 3 | | 16 | 程咬银 | female | 18 | 2013-03-11 | operation | NULL | 19000.00 | 403 | 3 | | 17 | 程咬铜 | male | 18 | 2015-04-11 | operation | NULL | 18000.00 | 403 | 3 | | 18 | 程咬铁 | female | 18 | 2014-05-12 | operation | NULL | 17000.00 | 403 | 3 | | 14 | 张野 | male | 28 | 2016-03-11 | operation | NULL | 10000.13 | 403 | 3 | | 8 | 成龙 | male | 48 | 2010-11-11 | teacher | NULL | 10000.00 | 401 | 1 | | 6 | jingliyang | female | 18 | 2011-02-11 | teacher | NULL | 9000.00 | 401 | 1 | | 3 | wupeiqi | male | 81 | 2013-03-05 | teacher | NULL | 8300.00 | 401 | 1 | | 1 | egon | male | 18 | 2017-03-01 | 老男孩驻沙河办事处外交大使 | NULL | 7300.33 | 401 | 1 | | 13 | 格格 | female | 28 | 2017-01-27 | sale | NULL | 4000.33 | 402 | 2 | | 4 | yuanhao | male | 73 | 2014-07-01 | teacher | NULL | 3500.00 | 401 | 1 | | 12 | 星星 | female | 18 | 2016-05-13 | sale | NULL | 3000.29 | 402 | 2 | | 9 | 歪歪 | female | 48 | 2015-03-11 | sale | NULL | 3000.13 | 402 | 2 | | 5 | liwenzhou | male | 28 | 2012-11-01 | teacher | NULL | 2100.00 | 401 | 1 | | 10 | 丫丫 | female | 38 | 2010-11-01 | sale | NULL | 2000.35 | 402 | 2 | | 11 | 丁丁 | female | 18 | 2011-03-12 | sale | NULL | 1000.37 | 402 | 2 | +----+------------+--------+-----+------------+-----------------------------------------+--------------+------------+--------+-----------+ 18 rows in set (0.00 sec)
limit 限制查询的记录数
limit 限制查询的记录数 limit n 取前n个值 limit m,n 从m+1的位置开始,取n条数据 应用: 分页显示 limit n offset m 从m+1的位置开始,取n条数据
# 分页显示 每页显示5条数据 mysql> select * from employee limit 5; +----+-----------+------+-----+------------+-----------------------------------------+--------------+------------+--------+-----------+ | id | emp_name | sex | age | hire_date | post | post_comment | salary | office | depart_id | +----+-----------+------+-----+------------+-----------------------------------------+--------------+------------+--------+-----------+ | 1 | egon | male | 18 | 2017-03-01 | 老男孩驻沙河办事处外交大使 | NULL | 7300.33 | 401 | 1 | | 2 | alex | male | 78 | 2015-03-02 | teacher | NULL | 1000000.31 | 401 | 1 | | 3 | wupeiqi | male | 81 | 2013-03-05 | teacher | NULL | 8300.00 | 401 | 1 | | 4 | yuanhao | male | 73 | 2014-07-01 | teacher | NULL | 3500.00 | 401 | 1 | | 5 | liwenzhou | male | 28 | 2012-11-01 | teacher | NULL | 2100.00 | 401 | 1 | +----+-----------+------+-----+------------+-----------------------------------------+--------------+------------+--------+-----------+ 5 rows in set (0.01 sec)mysql> select * from employee limit 5,5; +----+------------+--------+-----+------------+---------+--------------+----------+--------+-----------+ | id | emp_name | sex | age | hire_date | post | post_comment | salary | office | depart_id | +----+------------+--------+-----+------------+---------+--------------+----------+--------+-----------+ | 6 | jingliyang | female | 18 | 2011-02-11 | teacher | NULL | 9000.00 | 401 | 1 | | 7 | jinxin | male | 18 | 1900-03-01 | teacher | NULL | 30000.00 | 401 | 1 | | 8 | 成龙 | male | 48 | 2010-11-11 | teacher | NULL | 10000.00 | 401 | 1 | | 9 | 歪歪 | female | 48 | 2015-03-11 | sale | NULL | 3000.13 | 402 | 2 | | 10 | 丫丫 | female | 38 | 2010-11-01 | sale | NULL | 2000.35 | 402 | 2 | +----+------------+--------+-----+------------+---------+--------------+----------+--------+-----------+ 5 rows in set (0.00 sec)
关键字执行顺序 : from > where > group by > select > having >order by > limit
