MYSQL 使用语句总结

  • 数据库操作:
  create database db_name charset utf8;#创建数据库  drop database db_name;#删除数据库  use db_name;#切换数据库  show databases;#查看所有数据库 
表操作:
  创建表:
  数据类型:    整形:      tinyint smallint int bigint     浮点型:       float double    字符串:      char varchar text    日期类型:      date datetime timestamp 
  约束:
    1、主键约束  唯一、非空  primary key    2、外键约束  foreign key     3、唯一约束  unique    4、非空约束  not null    5、默认值约束 default    6、自增长  auto_increment
  DDL、DCL、DML语句:
    DDL:      数据定义语句  create、drop、alter    DML:      数据操纵语句  select、insert、update、delete     DCL:      数据控制语句  grant 
  建表
      create table student (        id int primary key auto_increment,        name varchar(20) not null ,        phone varchar(11) unique not null,        sex tinyint default 0,        addr varchar(50),        brith datetime default current_timestamp,        index(name)        );       create table score (        id int primary key auto_increment,        score float not null,        sid int not null        );     create table student_new like student; -- 快速创建一个和student表结构一样的表 
  修改表:
      alter table student add class2 int not null; -- 增加字段      alter table student drop addr; -- 删除字段      alter table student change name new_name varchar(20) not null; -- 修改字段      alter table student modify  name varchar(30) ;
  删除表:
    drop table student;
  清空表:
    truncate table student; -- 自增长id会重新开始
  其他操作:
     show tables;-- 查看当前所有表     show create table student; -- 查看建表语句     desc student; -- 查看表结构  
  数据操作:
    增:
      insert into student values ('','python','11111111111',0,'北京','2019-01-03 18:39:23'); --写全      insert into student  (name,phone) values ('mysql','12345678901'); -- 指定字段      insert into student  (name,phone) values ('mysql1','12345678902'),('mysql2','22345678901'); --多条      insert into student_new select * from student; -- 把一个表的数据快速导出到另外一个表
    修改:
      update student set name='mysql3' ; --修改全表数据      update student set name'mysql2',sex=1; --修改多个字段      update student set name='mysql3' where id = 1; #指定修改某条数据
    删除:
      delete from student; --整表数据删除      delete from student where id = 3; --指定数据删除 
    查询:
     基本查询     select * from student;     select id,name,addr from student; --指定字段     select id as 编号, addr 地址 , name 姓名 from student; --字段加别名          where条件     select * from student where id=1; --where条件 >,<,>=,<=,!=,<>     select * from student where id in (1,2,3) and id != 5; -- in和and条件     select * from student where id between 1 and 5; -- 范围     select * from student where id between 1 and 5 or id > 10; -- or          排序     select * from student where id between 1 and 5 order by id desc; -- 一起用的话,order by必须写在where条件后面     select * from student order by id desc ;  -- 降序排序,按照id,升序的话是asc     select * from student order by id,name  asc ;  -- 升序,按照id和name排序,asc可以省略不写          分组     select * from student group by sex; -- 按照某个字段分组,可以写多个字段     select * from student group by sex having addr !='北京';     select * from student where id >5  group by sex having addr !='北京'; -- 如果有where条件,必须写在group by前面,group by后面不能再写where条件,如果有条件必须用having子句      limit     select id as 编号, addr 地址 , name 姓名 from student limit 2; -- 前N条数据     select id as 编号, addr 地址 , name 姓名 from student limit 1,5; -- 从第一行开始,向后取5行,不包含第一行的数据     select * from student where id >0  group by sex having addr !='北京'  limit 5; -- limit必须写在最后面     select * from student where id >0  group by sex having addr !='北京'  order by id desc limit 5; -- limit必须写在最后面     #如果一个sql里面有where、group by、排序、limit,顺序一定是1、where 2、group by 3、order by 4、limit      聚合函数     select count(*) from student; -- 多少条数据     select count(addr) from student; -- 某个字段不为空的有多少条     select count(*) 人数 ,sex 性别 from student group by sex; -- 多少条数据     select avg(age) from student; -- 平均值     select sum(score) from score;  -- 和     select min(score) from score;      select max(score) from score;       子查询      select * from student where id in (select sid from score where score >= 60);      多表查询     select * from student a ,score b where a.id = b.sid and a.score>90;          select a.name,b.score,a.class2 from student a ,score b where a.id = b.sid and a.score>90;      select a.name ,b.score,a.class2 from student a inner join score b  on a.id = b.sid  where a.score > 90;      select a.name ,b.score,a.class2 from student a left join score b  on a.id = b.sid  where a.score > 90; 
    授权
      GRANT ALL privileges ON *.* TO 'root'@'localhost' IDENTIFIED BY '123456';      GRANT ALL privileges ON byz.* TO 'byz'@'%' IDENTIFIED BY '123456';      flush privileges; 
發表評論
所有評論
還沒有人評論,想成為第一個評論的人麼? 請在上方評論欄輸入並且點擊發布.
相關文章