create database db_name charset utf8;#創建數據庫 drop database db_name;#刪除數據庫 use db_name;#切換數據庫 show databases;#查看所有數據庫
表操作：
創建表：
數據類型： 整形： tinyint smallint int bigint 浮點型： float double 字符串： char varchar text 日期類型： date datetime timestamp
約束：
1、主鍵約束 唯一、非空 primary key 2、外鍵約束 foreign key 3、唯一約束 unique 4、非空約束 not null 5、默認值約束 default 6、自增長 auto_increment
DDL、DCL、DML語句：
DDL： 數據定義語句 create、drop、alter DML： 數據操縱語句 select、insert、update、delete DCL： 數據控制語句 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; -- 快速創建一個和student表結構一樣的表
修改表：
alter table student add class2 int not null; -- 增加字段 alter table student drop addr; -- 刪除字段 alter table student change name new_name varchar(20) not null; -- 修改字段 alter table student modify name varchar(30) ;
刪除表：
drop table student；
清空表：
truncate table student; -- 自增長id會重新開始
其他操作：
show tables；-- 查看當前所有表 show create table student; -- 查看建表語句 desc student; -- 查看錶結構
數據操作：
增：
insert into student values ('','python','11111111111',0,'北京','2019-01-03 18:39:23'); --寫全 insert into student (name,phone) values ('mysql','12345678901'); -- 指定字段 insert into student (name,phone) values ('mysql1','12345678902'),('mysql2','22345678901'); --多條 insert into student_new select * from student; -- 把一個表的數據快速導出到另外一個表
修改：
update student set name='mysql3' ; --修改全表數據 update student set name'mysql2',sex=1; --修改多個字段 update student set name='mysql3' where id = 1; #指定修改某條數據
刪除：
delete from student; --整表數據刪除 delete from student where id = 3; --指定數據刪除
查詢：
基本查詢 select * from student; select id,name,addr from student; --指定字段 select id as 編號, addr 地址 , name 姓名 from student; --字段加別名 where條件 select * from student where id=1; --where條件 >,<,>=,<=,!=,<> select * from student where id in (1,2,3) and id != 5; -- in和and條件 select * from student where id between 1 and 5; -- 範圍 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; -- 一起用的話，order by必須寫在where條件後面 select * from student order by id desc ; -- 降序排序，按照id，升序的話是asc select * from student order by id,name asc ; -- 升序，按照id和name排序，asc可以省略不寫 分組 select * from student group by sex; -- 按照某個字段分組，可以寫多個字段 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條件，必須寫在group by前面，group by後面不能再寫where條件，如果有條件必須用having子句 limit select id as 編號, addr 地址 , name 姓名 from student limit 2; -- 前N條數據 select id as 編號, addr 地址 , name 姓名 from student limit 1,5; -- 從第一行開始，向後取5行，不包含第一行的數據 select * from student where id >0 group by sex having addr !='北京' limit 5; -- limit必須寫在最後面 select * from student where id >0 group by sex having addr !='北京' order by id desc limit 5; -- limit必須寫在最後面 #如果一個sql裏面有where、group by、排序、limit，順序一定是1、where 2、group by 3、order by 4、limit 聚合函數 select count(*) from student; -- 多少條數據 select count(addr) from student; -- 某個字段不爲空的有多少條 select count(*) 人數 ,sex 性別 from student group by sex; -- 多少條數據 select avg(age) from student; -- 平均值 select sum(score) from score; -- 和 select min(score) from score; select max(score) from score; 子查詢 select * from student where id in (select sid from score where score >= 60); 多表查詢 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;
授權
GRANT ALL privileges ON *.* TO 'root'@'localhost' IDENTIFIED BY '123456'; GRANT ALL privileges ON byz.* TO 'byz'@'%' IDENTIFIED BY '123456'; flush privileges;
