mysql 常用总结

centos7 安装mysql

数据库安装参考：
http://www.cnblogs.com/longrui/p/6071581.html
https://www.cnblogs.com/yoursoul/p/6264059.html

ERROR 1819 (HY000): Your password does not satisfy the current policy requirements

http://www.zhimengzhe.com/shujuku/MySQL/89138.html

1、进入information_schema 数据库

use information_schema;

2、查询所有数据的大小：

select concat(round(sum(data_length/1024/1024),2),'MB') as data from tables;

3、查看指定数据库的大小：

比如查看数据库home的大小

select concat(round(sum(data_length/1024/1024),2),'MB') as data from tables where table_schema='home';

4、查看指定数据库的某个表的大小

比如查看数据库home中 members 表的大小

select concat(round(sum(data_length/1024/1024),2),'MB') as data from tables where table_schema='home' and table_name='members';

5、查看表和索引占用空间

select concat(round(sum(data_length/1024/1024),2),'MB') as data_length_MB,concat(round(sum(index_length/1024/1024),2),'MB') as index_length_MB  from tables where table_schema='task_db' and table_name = 'adclick_table'; 

6、查看某库下所有表的大小

select table_schema,table_name,concat(round(DATA_LENGTH/1024/1024,2),'MB') as data from tables where table_schema='数据库名' order by data_length desc;

创建库

create database task;
use task;
alter database task character set utf8;
grant all privileges on task.* to 'root'@'%' identified by 'password';

 7、导库数据

数据导出

mysqldump -uroot -p databasename > databasename.sql

数据导入
use dbname;
source databasename.sql

创建索引：

ALTER TABLE `table_name` ADD INDEX index_id ( `id` )

查看索引：

show index from import_data

随机取一条数据：

SELECT * FROM import_data  AS t1 JOIN (SELECT ROUND(RAND() * (SELECT MAX(id) FROM import_data)) AS id) AS t2 WHERE t1.id >= t2.id ORDER BY t1.id ASC LIMIT 1

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数据库锁住处理

查看所有进程

 show full processlist;

查看所有事物

 select * from information_schema.innodb_trx;

如果有锁住的，kill 掉

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mysql 8.0.12 修改root密码

use mysql；
ALTER USER 'root'@'localhost' IDENTIFIED WITH mysql_native_password BY '新密码';
FLUSH PRIVILEGES;

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