话不多说直接来，后续补充。
查看数据库
show databases;
创建数据库
create database 2018;
使用数据库
use 2018;
查看数据库中的所有表
show tables;
删除数据库
drop database 库名;
create table student(
id int(10) auto_increment primary key,
name varchar(20) not null,
age int(5) default 16,
address char(50);
)
查看表设计
desc student;
添加数据 不按照字段体添加 所有字段需要定义
insert into student values(1,'张三'，20，‘北京’);
不常用
按照字段添加
insert into student(name,age,address) values('李四'，22，'北京');
insert into student(name) values('王五')；
insert into student(name，age,address) values('赵六',29,'上海')，
('赵晓晓',24,'深圳'),('张红',21,'北京'),('赵晓刘',23,'深圳');
删除
delete from student where id =3;
delete from student where age=24;
delete from student where age=26 and ='赵六';
将表中的数据删除 表仍然在
delete from student;
删除表
drop table student;
修改
update student set age =26,address='上海' where name='王五';
update student set age =26,address='上海';
查询* 表中的所有内容
select * from student;
查询年龄在20-26之间的学生和年龄 between。。。and
select name,age from student where age between 20 and 26;
模糊查询 like %代表多个字符
select name from student where name like '李%'；
# _代表的为一个字符
select name from student where name like '李_';
select name from student where name like '%小%';
select name,age,address from student where name like '%六';
#查询ID为偶数的学生信息
select * from student where id%2=0;
#查询年龄不等于23的学生姓名和年龄 两种写法 != ,<>
select name,age from student where age !=23;
select name,age from student where age <>23;
#查询id 为3,6，7,10 in包含
select * from student where id in(10,6,7,3);
#查询年龄26 并且上海 and
select * from student where age = 26 and address='上海';
#查询年龄26 或者来自上海
select * from student where age = 26 or address='上海';
#分页 显示第一页代表的是索引 每页显示3条 每次显示的条数
select * from student limit 3,3;
select * from student limit 4,2;
#查询和李四年龄相同的学生姓名
select name from student where age = (select age from student where name='李四') and name !='李四';
#将年龄从小到大排序
select * from student order by age;
#大到小排序 order by.. desc order by asc(小到大)
select * from student order by age desc;
#聚合函数
count(),sum(),avg.max().min()
#统计表中总数量
select count(id) from student;
select count(*) from student;
select count(1) from student;
#年龄的总和
select sum(age) from student;
#平均年龄
select avg(age) from student;
#获取最大值
select max(age) from student;
#获取最小值
select min(age) from student;
#统计每个年龄分布有多少人 group by 分组
select count(id),age from student group by age;
#group by 需要与聚合函数联合使用 having 必须与group by一起使用 为分组进行条件判断
select count(id),age from student group by age having age>20;
将地址分组查询
select count(id),address from student group by address;
统计同一地方人数大于3
select count(id),address from student group by address having count(id) >3;
select count(id) he,address from student group by address having he >3;
select count(id) as he,address from student group by address having he>3;
select count(id) as '总数',address from student group by address having 总数>3;
