MysqlDBA运维命令大全

Posted 2022-10-25

作者：IT邦德
中国DBA联盟(ACDU)成员，目前从事DBA及程序编程
（Web\\java\\Python）工作，主要服务于生产制造
现拥有 Oracle 11g  OCP/OCM、
mysql、Oceanbase（OBCA）认证
分布式TBase\\TDSQL数据库、国产达梦数据库以及红帽子认证
从业8年DBA工作，在数据库领域有丰富的经验

1、 MySQL 的注释

MySQL 注释符有三种：
1、#...
2、"-- ..." （注意 -- 后面有一个空格）
3、/*...*/

2、 如何查看 MySQL 数据库的大小

查询所有数据的大小：
mysql> select concat(round(sum(data_length/1024/1024),2),MB) as data from information_schema.tables;

查看指定数据库的大小，例如查看数据库db_school 的大小：
select concat(round(sum(data_length/1024/1024),2),MB) as data 
from information_schema.tables where table_schema=db_school;

查看指定数据库的某个表的大小
例如查看数据库db_school 中 db_school表的大小：
select concat(round(sum(data_length/1024/1024),2),MB) as data 
from information_schema.tables 
where table_schema=db_school and table_name=db_school;

当前数据库实例的所有数据库及其容量大小：
select a.SCHEMA_NAME, a.DEFAULT_CHARACTER_SET_NAME,a.DEFAULT_COLLATION_NAME,
sum(table_rows) as 记录数,
sum(truncate(data_length/1024/1024, 2)) as 数据容量(MB),
sum(truncate(index_length/1024/1024, 2)) as 索引容量(MB),
sum(truncate((data_length+index_length)/1024/1024, 2)) as 总大小(MB),
sum(truncate(max_data_length/1024/1024, 2)) as 最大值(MB),
sum(truncate(data_free/1024/1024, 2)) as 空闲空间(MB)
from INFORMATION_SCHEMA.SCHEMATA a
left outer join information_schema.tables b
on a.SCHEMA_NAME=b.TABLE_SCHEMA
group by a.SCHEMA_NAME, a.DEFAULT_CHARACTER_SET_NAME,a.DEFAULT_COLLATION_NAME
order by sum(data_length) desc, sum(index_length) desc;

占用空间最大的前 10 张表
SELECT
table_schema AS 数据库,
table_name AS 表名,
a.TABLE_TYPE,
a.`ENGINE`,
a.CREATE_TIME,
a.UPDATE_TIME,
a.TABLE_COLLATION,
table_rows AS 记录数,
TRUNCATE ( data_length / 1024 / 1024, 2 ) AS 数据容量(MB),
TRUNCATE ( index_length / 1024 / 1024, 2 ) AS 索引容量(MB),
TRUNCATE ( ( data_length + index_length ) / 1024 / 1024, 2 ) AS 总大小(MB)
FROM information_schema.TABLES a
ORDER BY ( data_length + index_length ) DESC
LIMIT 10;

查询数据库对象：
select db as 数据库,type as 对象类型,cnt as 对象数量 from
(select TABLE type,table_schema db, count(*) cnt from information_schema.`TABLES` a where table_type=BASE TABLE group by table_schema
union all
select EVENTS type,event_schema db,count(*) cnt from information_schema.`EVENTS` b group by event_schema
union all
select TRIGGERS type,trigger_schema db,count(*) cnt from information_schema.`TRIGGERS` c group by trigger_schema
union all
select PROCEDURE type,routine_schema db,count(*) cnt from information_schema.ROUTINES d where`ROUTINE_TYPE` = PROCEDURE group by db
union all
select FUNCTION type,routine_schema db,count(*) cnt from information_schema.ROUTINES d where`ROUTINE_TYPE` = FUNCTION group by db
union all
select VIEWS type,TABLE_SCHEMA db,count(*) cnt from information_schema.VIEWS f group by table_schema ) t
order by db,type;

*3.如何查看 MySQL 的版本？

有如下几种办法：
① mysql -V
② mysql> show variables like %version_%;
③ which mysql |xargs file （linux/unix 系统）
④ echo STATUS|mysql -uroot -ppassword |grep

本文如有错误或不完善的地方请大家多多指正，微信留言或 QQ 皆可，您的批评指正是我写作的最大动力!