MySQL语法大全_自己整理的学习笔记（MySQL语句整理二）

女爷i 2022-01-06 11:35 367阅读 0赞

desc 表名;
    查看表结构
    desc 表名 \G;
    查看详细结构
    
    
    
    
    select * from emp;  #注释
    #---------------------------
    #----命令行连接MySql---------
     
    #启动mysql服务器
    net start mysql
     
    #关闭 
    net stop mysql
      
    #进入
    mysql -h 主机地址 -u 用户名 －p 用户密码
     
    #退出
    exit
    
    status;
    显示当前mysql的version的各种信息。
     
    #---------------------------
    #----MySql用户管理---------
     
    #修改密码:首先在DOS 下进入mysql安装路径的bin目录下，然后键入以下命令:
    mysqladmin -uroot -p123 password 456;
     
    #增加用户
    #格式:grant 权限 on 数据库.* to 用户名@登录主机 identified by '密码'
    /*
    如，增加一个用户user1密码为password1，让其可以在本机上登录， 并对所有数据库有查询、插入、修改、删除的权限。首先用以root用户连入mysql，然后键入以下命令：
    grant select,insert,update,delete on *.* to user1@localhost Identified by "password1";
    如果希望该用户能够在任何机器上登陆mysql，则将localhost改为"%"。
    如果你不想user1有密码，可以再打一个命令将密码去掉。
    grant select,insert,update,delete on mydb.* to user1@localhost identified by "";
    */
     
    grant all privileges on wpj1105.* to sunxiao@localhost identified by '123';   #all privileges 所有权限
     
    #----------------------------
    #-----MySql数据库操作基础-----
     
    #显示数据库
    show databases;
     
    #判断是否存在数据库wpj1105,有的话先删除
    drop database if exists wpj1105;
     
    #创建数据库
    create database wpj1105;
     
    #删除数据库
    drop database wpj1105;
     
    #使用该数据库
    use wpj1105;
     
    #显示数据库中的表
    show tables;
     
    #先判断表是否存在,存在先删除
    drop table if exists student;
     
    #创建表
    create table student(
    id int auto_increment primary key,
    name varchar(50),
    sex varchar(20),
    date varchar(50),
    content varchar(100)
    )default charset=utf8;
     
    #删除表
    drop table student;
     
    #查看表的结构
    describe student;  #可以简写为desc student;
     
    #插入数据
    insert into student values(null,'aa','男','1988-10-2','......');
    insert into student values(null,'bb','女','1889-03-6','......');
    insert into student values(null,'cc','男','1889-08-8','......');
    insert into student values(null,'dd','女','1889-12-8','......');
    insert into student values(null,'ee','女','1889-09-6','......');
    insert into student values(null,'ff','null','1889-09-6','......');
    #查询表中的数据
    select * from student;
    select id,name from student;
     
    #修改某一条数据
    update student set sex='男' where id=4;
     
    #删除数据
    delete from student where id=5;
     
    # and 且
    select * from student where date>'1988-1-2' and date<'1988-12-1';
     
    # or 或
    select * from student where date<'1988-11-2' or date>'1988-12-1';
      
    #between
    select * from student where date between '1988-1-2' and '1988-12-1';
     
    #in 查询制定集合内的数据
    select * from student where id in (1,3,5);
     
    #排序 asc 升序  desc 降序
    select * from student order by id asc;
     
    #分组查询 #聚合函数
    select max(id),name,sex from student group by sex;
     
    select min(date) from student;
     
    select avg(id) as '求平均' from student;
     
    select count(*) from student;   #统计表中总数
     
    select count(sex) from student;   #统计表中性别总数  若有一条数据中sex为空的话,就不予以统计~
     
    select sum(id) from student;
     
    #查询第i条以后到第j条的数据(不包括第i条)
    select * from student limit 2,5;  #显示3-5条数据
     
    #巩固练习
    create table c(
     id int primary key auto_increment,
     name varchar(10) not null,
     sex varchar(50) ,  #DEFAULT '男' ,
     age int unsigned, #不能为负值(如为负值 则默认为0)
     sno int unique    #不可重复
    );
     
    drop table c;
    desc c;
     
    insert into c (id,name,sex,age,sno) values (null,'涛哥','男',68,1);
    insert into c (id,name,sex,age,sno) values (null,'aa','男',68,2);
    insert into c (id,name,sex,age,sno) values (null,'平平','男',35,3);
    ...
     
    select * from c;
     
    #修改数据
    update c set age=66 where id=2;
    update c set name='花花',age=21,sex='女' where id=2
    delete from c where age=21;
     
    #常用查询语句
    select name,age ,id from c
    select * from c where age>40 and age<60;  #and
    select * from c where age<40 or age<60;  #or
    select * from c where age between 40 and 60 #between
    select * from c where age in (30,48,68,99);     #in 查询指定集合内的数据
    select * from c order by age desc;      #order by （asc升序 des降序）
     
    #分组查询
    select name,max(age) from c group by sex;  #按性别分组查年龄最大值
    #聚合函数
    select min(age) from c;
    select avg(age) as '平均年龄 ' from c;
    select count(*) from c;  #统计表中数据总数
    select sum(age) from c;
     
    #修改表的名字
    #格式:alter table tbl_name rename to new_name
    alter table c rename to a;
      
    #表结构修改
    create table test
    (
    id int not null auto_increment primary key, #设定主键
    name varchar(20) not null default 'NoName', #设定默认值
    department_id int not null,
    position_id int not null,
    unique (department_id,position_id) #设定唯一值
    );
     
    #修改表的名字
    #格式:alter table tbl_name rename to new_name
    alter table test rename to test_rename;
     
    #向表中增加一个字段(列)
    #格式:alter table tablename add columnname type;/alter table tablename add(columnname type);
    alter table test add  columnname varchar(20);
     
    #修改表中某个字段的名字
    alter table tablename change columnname newcolumnname type;  #修改一个表的字段名
    alter table test change name uname varchar(50);
     
    select * from test;
     
    #表position 增加列test
    alter table position add(test char(10));
    #表position 修改列test
    alter table position modify test char(20) not null;
    #表position 修改列test 默认值
    alter table position alter test set default 'system';
    #表position 去掉test 默认值
    alter table position alter test drop default;
    #表position 去掉列test
    alter table position drop column test;
    #表depart_pos 删除主键
    alter table depart_pos drop primary key;
    #表depart_pos 增加主键
    alter table depart_pos add primary key PK_depart_pos
    (department_id,position_id);
     
    #用文本方式将数据装入数据库表中（例如D:/mysql.txt）
    load data local infile "D:/mysql.txt" into table MYTABLE;
     
    #导入.sql文件命令（例如D:/mysql.sql）
    source d:/mysql.sql;  #或者  /. d:/mysql.sql;

转载于:https://www.cnblogs.com/jasonLiu2018/articles/10702322.html