mysql如何快速查詢

mysql快速查詢的方法：1、查詢正在運行中的事務；2、查看當前連接，並且能夠知曉連接數；3、查看一個表的大小；4、查看某個資料庫所有表的大小。

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mysql快速查詢的方法：

1.查詢正在執行中的交易

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;

2.查看目前連接，並且能夠知道連接數

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

3 .查看一個表的大小

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‘;

4.查看某個資料庫所有表的大小

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

5.查看庫的大小，剩餘空間的大小

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;

6.尋找關於鎖定

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

information_schema的使用

1.查看各個庫下的表資料大小

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;

2.查看各個資料庫的資料大小

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

3.查看實例有沒有主鍵

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‘);

4.查看實例中哪些欄位可以為null

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

5.查看實例中有哪些預存程序和函數

#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‘);

6.查看實例中哪些表格欄位字元集和預設字元集不一致

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‘);

7.查看實例中哪些表格欄位字元校驗規則和預設的不一致

查看目前字元集和校對規則設定

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‘);

8.查看哪些帳號有除了select、update、insert以外的權限

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‘);

9.查看實例中哪些資料表不是預設儲存引擎，以預設儲存引擎為innodb為例

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

10.查看實例中哪些表有外鍵

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‘;

11.查看實例中哪些表格欄位有級聯更新

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‘);

12.如何根據使用者名稱、連接時間、執行的sql等過濾目前實例中的連接資訊

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

13.查看資料庫中沒有索引的表

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‘);

14.查看資料庫中有索引的表，建立了哪些索引

顯示結果：庫名、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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