1.登录mysql：
mysql -u root -p
2.查看mysql中有多少数据库
show databases;
3.查看当前数据库名称
select database();
4.切换数据库
use databasename
5.查看数据库中有多少表格
show tables;
6.查看表结构
desc tablename;
7.创建数据库
create database databasename;
8.创建表格
create table tablename(
列名(字段) 数据类型，
列名(字段) 数据类型,
......
);
9.向表格增加数据
insert into tablename(列名1，列名2) values(值1,值2..),(值1，值2)(值1，值2);
10.向表格增加列
alter table tablename add column columnname 数据类型;
11.删除表格数据,不改变表结构（删除行？）
delete from tablename where (过滤条件)
12.删除表格的全部数据，不改变表结构
truncate tablename
13.删除表格
drop table tablename
14.删除列结构
alter tablename drop column columnname;
15.修改表名
rename table oldtablename to newtablename;
16.移动表格到其他数据库
rename table olddb.tablename to newdb.tablename;
17.修改列属性(新名同旧名，也能达到修改列名的目的)
alter table tablename change columnname_old columnname_new type;
18.修改列属性
alter table tablename modify columnname newtype
19.查询表格所有数据
select * from tablename
20.查询表格某项数据
select columnname from tablename where (过滤条件)
21.模糊查询
select * from tablename where columnname like "d%";查询以d开头的数据，%表示多个字符
select * from tablename where columnname like "d_";查看以d开的两个字符的数据，_表示一个字符
select * from kr where pname like '____';查询表中4隔字符的数据
22.空值查询
select * from tablename where columnname is null;查询值为空的数据
select * from tablename where columnname is not null;查询值不为空的数据
23.范围查询
select * from tablename where columnname in('gaga','baga');#in与括号间没有空格
24.比较运算符
select pname from kr where price>260;大于
select * from kr where pname <>'heyga';不等于
select * from kr where pname !='heyga';不等于
25.逻辑运算符:and ,or, between....and
select * from kr where price <=250 and pname='simida';
select * from kr where pname='simida' or pname='heygor';
select * from kr where price >=250 and price <=290;
select * from kr where price between 250 and 290;
26.多表查询
26.1内关联
select * from tablename1,tablename2 where tablename1.column=tablename2.column;
26.2左关联
select * from tableleft left join tableright where tableleft.column=tableright.column;
26.3右关联
select 列 from 左表 right join 右表 on 左表.列=右表.列;
27.子查询
select city from city where country_id=(select country_id from country where country='China');
28.分组查询，where不可接count(),max().等条件，having可以
select 列 from 表 [where 条件] group by 分组条件 [having 分组后过滤条件];
select count(first_name) from customer,country,address,city where customer.address_id=address.address_id and address.city_id=city.city_id and city.country_id=country.country_id group by country.country having country='china';
28.分组函数(聚合)
max()
min()
avg()
sum()
count()
分组函数通常和分组一起使用，也可以单独使用
例子：查询payment表中最高金额，最低金额，平均金额
select max(amount),min(amount),avg(amount) from payment;
29.查询表格第一行
select * from tablename limit 1;
30.查询表格第2,3行;limit n-1,m-n+1
select * from exam limit 1,2;
31.查看表格最后一行
select * from exam order by linux desc limit 1;
32.查询后几行
select * from exam order by linux desc limit n；//倒序排序，取前n行 id为自增形式
查询一条记录($id)的下一条记录
select * from table1 where id>20 order by id asc dlimit 1 ; //正序排序
查询一条记录($id)的上一条记录
select * from table1 where id<$id order by id desc dlimit 1;//倒序排序
select * from exam where linux=(select linux from exam where linux>{$linux} order by linux asc limit 1);