mysql初级

★

mysql客户端 <=> mysqld.exe服务器端[24小时在运行] 存取数据是这两个在通话

查看库 show databases; 选库 use test; 查看库下的表 show tables; 查表 select * from cat

DML,增删改查 -> 增

准备工作: 通过 phpmyadmin 导入”练习准备.sql”

desc user; uid name age 三列

insert into user (uid,name,age) values (1,'lisi',23);

insert into user (uid,name) values (1,'lucy');

insert into user (name) values ('yumi');

insert into user values ('kimi',25); //报错:

列计数不匹配值计数 insert into user values (3,'kimi',25);

字符串必须加单引号,不加会理解为一个列名或者变量,会报错

insert into user values ('4','zhangsan','25'); insert into user values (5,zhangsan,25);

insert into user values (5,'test1',44),(6,'test2',23),(7,'test3',18);

update 更改列

update user set age=99 where name='yumi';

update 表名 set 列1 = 新值1, 列2 = 新值2 where expr

1)sql是 what 型的语言,而不是how 如果是how,则需要这样写

for(所有行) { if(uid=2) { age = 23;

name = 'nobody'; } }

what型

update user set age=23,name='nobody' where uid=2;

我们不用管它内部如何去做,只告诉它我们需要怎么修改即可

update user set name='mingming', age=55;

delete from 表名 where expr

*sql: *

delete from user where uid=7;

注意不加where条件

delete from user;

select 列1,列2,...列n from 表名 where expr

select * from user;

select * from user where uid=2;

select * from user where uid>=2;

select uid,name from user where uid>=2; select name from user where uid=2;

建库: create database XXX; 选库: use XXX; 建表:

create table msg ( id int primary key auto_increment, title varchar(20), content varchar(100) ) charset utf8;