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mysql如何快速查询

coldplay.xixi

发布： 2020-11-13 10:09:25

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mysql快速查询的方法：1、查询正在运行中的事务；2、查看当前连接，并且能够知晓连接数；3、查看一个表的大小；4、查看某个数据库所有表的大小。

mysql如何快速查询

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mysql快速查询的方法：

1.查询正在运行中的事务

select p.id,p.user,p.host,p.db,p.command,p.time,i.trx_state,i.trx_started,p.info  from information_schema.processlist p,information_schema.innodb_trx i where p.id=i.trx_mysql_thread_id;

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2.查看当前连接，并且能够知晓连接数

select SUBSTRING_INDEX(host,‘:‘,1) as ip , count(*) from information_schema.processlist group by ip;

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3.查看一个表的大小

select concat(round(sum(DATA_LENGTH/1024/1024),2),‘M‘) from information_schema.tables where table_schema=‘数据库名‘ AND table_name=‘表名‘;

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4.查看某个数据库所有表的大小

select table_name,concat(round(sum(DATA_LENGTH/1024/1024),2),‘M‘)  from information_schema.tables where table_schema=‘t1‘ group by table_name;

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5.查看库的大小，剩余空间的大小

select table_schema,round((sum(data_length / 1024 / 1024) + sum(index_length / 1024 / 1024)),2) dbsize,round(sum(DATA_FREE / 1024 / 1024),2) freesize,       
round((sum(data_length / 1024 / 1024) + sum(index_length / 1024 / 1024)+sum(DATA_FREE / 1024 / 1024)),2) spsize  
from information_schema.tables 
where table_schema not in (‘mysql‘,‘information_schema‘,‘performance_schema‘) 
group by table_schema order by freesize desc;

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6.查找关于锁

select r.trx_id waiting_trx_id,r.trx_mysql_thread_id waiting_thread,r.trx_query waiting_query,b.trx_id blocking_trx_id,b.trx_mysql_thread_id blocking_thread,b.trx_query blocking_query  
from information_schema.innodb_lock_waits w 
inner join information_schema.innodb_trx b 
on b.trx_id = w.blocking_trx_id 
inner join information_schema.innodb_trx r on r.trx_id = w.requesting_trx_id\G

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information_schema的使用

1.查看各个库下的表数据大小

select table_name,concat(round(sum(DATA_LENGTH/1024/1024),2),‘M‘) 
from information_schema.tables where table_schema=‘db_name‘ group by table_name;

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2.查看各个数据库的数据大小

select TABLE_SCHEMA, concat(round(sum(data_length)/1024/1024,2),‘ MB‘) as data_size  from information_schema.tables group by table_schema;

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3.查看实例有没有主键

select table_schema,table_name from information_schema.tables 
where (table_schema,table_name) 
not in(select distinct table_schema,table_name from information_schema.STATISTICS where INDEX_NAME=‘PRIMARY‘ ) 
and table_schema not in ( ‘sys‘,‘mysql‘,‘information_schema‘,‘performance_schema‘);

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4.查看实例中哪些字段可以为null

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select TABLE_SCHEMA,TABLE_NAME from COLUMNS where IS_NULLABLE=‘YES‘ and TABLE_SCHEMA not in (‘information_schema‘,‘performance_schema‘,‘mysql‘, ‘sys‘)\G

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5.查看实例中有哪些存储过程和函数

#存储过程
select ROUTINE_SCHEMA,ROUTINE_NAME,ROUTINE_TYPE
from information_schema.ROUTINES
where ROUTINE_TYPE=‘PROCEDURE‘ and ROUTINE_SCHEMA not in (‘mysql‘,‘sys‘,‘information_schema‘,‘performance_schema‘);
#函数
select ROUTINE_SCHEMA,ROUTINE_NAME,ROUTINE_TYPE 
from information_schema.ROUTINES 
where ROUTINE_TYPE=‘FUNCTION‘ and ROUTINE_SCHEMA not in (‘mysql‘,‘sys‘,‘information_schema‘,‘performance_schema‘);

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6.查看实例中哪些表字段字符集和默认字符集不一致

select TABLE_SCHEMA,TABLE_NAME,COLUMN_NAME,CHARACTER_SET_NAME 
from information_schema.COLUMNS 
where (CHARACTER_SET_NAME is null or CHARACTER_SET_NAME <> ‘utf8‘) 
and TABLE_SCHEMA not in (‘information_schema‘,‘performance_schema‘,‘test‘,‘mysql‘,‘sys‘);

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7.查看实例中哪些表字段字符校验规则和默认的不一致

查看当前字符集和校对规则设置

show variables like ‘collation_%‘;
select TABLE_SCHEMA,TABLE_NAME,COLUMN_NAME,CHARACTER_SET_NAME,COLLATION_NAME 
from information_schema.COLUMNS 
where (COLLATION_NAME is null or COLLATION_NAME <> ‘utf8_general_ci‘) 
and TABLE_SCHEMA not in (‘information_schema‘,‘performance_schema‘,‘test‘,‘mysql‘,‘sys‘);

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8.查看哪些账号有除了select、update、insert以外的权限

select GRANTEE,PRIVILEGE_TYPE,concat(TABLE_SCHEMA,‘-‘,TABLE_NAME,‘-‘,COLUMN_NAME) from COLUMN_PRIVILEGES where PRIVILEGE_TYPE not in (‘select‘,‘insert‘,‘update‘)
union 
select GRANTEE,PRIVILEGE_TYPE,TABLE_SCHEMA from SCHEMA_PRIVILEGES where PRIVILEGE_TYPE not in (‘select‘,‘insert‘,‘update‘)
union
select GRANTEE,PRIVILEGE_TYPE,concat(TABLE_SCHEMA,‘-‘,TABLE_NAME) from TABLE_PRIVILEGES where PRIVILEGE_TYPE not in (‘select‘,‘insert‘,‘update‘) 
union
select GRANTEE,PRIVILEGE_TYPE,concat(‘user‘) from USER_PRIVILEGES where PRIVILEGE_TYPE not in (‘select‘,‘insert‘,‘update‘);

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9.查看实例中哪些表不是默认存储引擎，以默认存储引擎为innodb为例

select TABLE_NAME,ENGINE 
from information_schema.tables 
where ENGINE!=‘innodb‘ and TABLE_SCHEMA not in (‘information_schema‘,‘performance_schema‘,‘test‘,‘mysql‘, ‘sys‘);

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10.查看实例中哪些表有外键

select a.TABLE_SCHEMA,a.TABLE_NAME,a.CONSTRAINT_TYPE,a.CONSTRAINT_NAME,b.REFERENCED_TABLE_NAME,b.REFERENCED_COLUMN_NAME 
from information_schema.TABLE_CONSTRAINTS a LEFT JOIN information_schema.KEY_COLUMN_USAGE b 
ON a.CONSTRAINT_NAME=b.CONSTRAINT_NAME where a.CONSTRAINT_TYPE=‘FOREIGN KEY‘;

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11.查看实例中哪些表字段有级联更新

select TABLE_SCHEMA,TABLE_NAME,COLUMN_NAME,REFERENCED_TABLE_SCHEMA,REFERENCED_TABLE_NAME,REFERENCED_COLUMN_NAME 
from information_schema.KEY_COLUMN_USAGE 
where REFERENCED_TABLE_SCHEMA is not null 
and REFERENCED_TABLE_NAME is not null 
and REFERENCED_COLUMN_NAME is not null and table_schema not in (‘information_schema‘,‘performance_schema‘,‘test‘,‘mysql‘, ‘sys‘);

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12.如何根据用户名、连接时间、执行的sql等过滤当前实例中的连接信息

select USER,HOST,DB from processlist where TIME>2;

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13.查看数据库中没有索引的表

select TABLE_SCHEMA,TABLE_NAME from information_schema.tables 
where TABLE_NAME  not in (select distinct(any_value(TABLE_NAME))  from information_schema.STATISTICS group by INDEX_NAME) 
and TABLE_SCHEMA not in (‘sys‘,‘mysql‘,‘information_schema‘,‘performance_schema‘);

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14.查看数据库中有索引的表，建立了哪些索引

显示结果：库名、表名、索引名

select TABLE_SCHEMA,TABLE_NAME,group_concat(INDEX_NAME) 
from  information_schema.STATISTICS where TABLE_SCHEMA not in (‘sys‘,‘mysql‘,‘information_schema‘,‘performance_schema‘)  group by TABLE_NAME ;

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