MySQL常见指令

DDL:数据定义语言，关键字create,drop,alter

登录MSY服务器：mysql -u root -p

创建数据库：create database dbname;

删除数据库：drop database dbname;

查看系统所有数据库：show databases;

选择需要操作的数据库：use dbname;

查看选中数据库中所有的表:show tables;

创建表：create table tablename(

column_name_1 column_type_1,

column_name_2 column_type_2,

);

删除表：drop table tablename;

查看表定义：desc tablename;

修改表：

修改字段类型：alter table tablename modify[column]column_definition[first|after col_name];

增加表字段：alter table tablename add[column]column_definition[first_after col_name];

删除表字段：alter table tablename drop[column]col_name;

字段改名：alter table tablename change[column]old_column_name column_definition[first|after col_name];

更改表名：alter table tablename rename[to]new_name;

DML:数据操作语言，对记录的操作,关键字insert,delect,update,select

插入记录：insert into tablename (field1,field2,....)values(values1,value2......),//插入一个记录

(values1,value2......);//插入多个记录

更新记录：update tablename set field1=value1,field2=value2,,,,fieldn=valuen[where condition];//更新一个表中记录

update tablename1,tablename2 set tablename1.field=expr1,tablename2.field=expr2,,,,[where condtion];//更新多个表中的记录

删除记录：delete from tablename [where condition]; //删除一个表中记录

delete a,b from tablename1 a,tablename2 b [where condition];

查询记录：select field from tablename;//普通查询

查询不重复的记录：select distinct field from tablename;

条件查询：select distinct field from tablename[where condition];

排序和限制：select field from tablename [where condition] [order by field1 [desc|asc],field2[desc|asc],,,] [limit offset_start,row_count];

聚合：select [field1,field2,,,,] fun_name //聚合操作

from tablename

[where where_condition]//进行分类聚合的字段

[group by field1,field2,,,]

[with rollup] //是否对聚合后的结果进行再汇总

[having where_condition] //是否对聚合后的结果进行条件过滤

表连接:同时显示多个表中的字段

内连接：select tablename1field ,tablename2field from tablename1,tablename2 where condition;

外连接（左连接）：select tablename1field,tablename2field from tablename1 left join tablename2 on where condition;

外连接（右连接）：select tablename1field,tablename2field from tablename1 right join tablename2 on where condition;

子查询：select field1,field2 from tablename1 in(select field from tableanme2);

记录联合：将多表的结果合并到一起显示。

select * from t1

union/union all

select * from t2

......

union/union all

select from tn;

DCL:管理系统中用户的权限，关键字grant,revoke.

授权：grant select on tablename.* to username identified by passwd;

收回：revoke select on tablename from username;