查看幫助命令

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MySQL> help; --總的幫助

mysql> help show; --查看show的幫助命令

mysql> help create;--查看create的幫助命令

mysql> help select;--查看select的幫助命令

mysql> help flush;--查看flush的幫助命令

mysql> help reset;--查看reset的幫助命令

查詢實(shí)例的基本信息

status

查看數(shù)據(jù)庫db1的創(chuàng)建腳本

mysql> show create database db1;

查看表table1的創(chuàng)建腳本

mysql> show create table table1\G 

查詢table1表哪些字段有索引，Key有值代表該字段有索引

desc table1

查詢table1表的索引，還能看到cardinality信息

show index from table1

查看select語句的執(zhí)行計(jì)劃

explain extended select * from t1;

desc extended select * from t1;

查看某個(gè)參數(shù)

show global variables like '%XX%';

show global variables where variable_name in ('XX');

查看數(shù)據(jù)庫是否只讀

show variables like 'read_only';

查看某個(gè)狀態(tài)

show status like '%YY%';

查看當(dāng)前連接的客戶端數(shù)量

show status like 'Threads_connected';

查看服務(wù)器的連接次數(shù)

show status like 'Connections';

查看曾經(jīng)的最大連接數(shù)

show status like 'Max_used_connections';

查看mysql線程

show full processlist;

查看有多少個(gè)數(shù)據(jù)庫

show databases;

查看當(dāng)前數(shù)據(jù)庫下有多少張表

show tables;

查看各種引擎信息,Support列為DEFAULT表示為當(dāng)前實(shí)例的默認(rèn)存儲(chǔ)引擎

show engines;

查看當(dāng)前實(shí)例的存儲(chǔ)引擎設(shè)置

show variables like '%engi%'

查看LSN(Log sequence number當(dāng)前redo log的最新號(hào))

show engine innodb status;

查看當(dāng)前數(shù)據(jù)庫

select database();

查看當(dāng)前數(shù)據(jù)庫服務(wù)器版本

select version();

查看當(dāng)前用戶

select user();

查詢未提交會(huì)話的具體SQL

show engine innodb status;查看lock struct信息，比如下面查看到線程是8

1 lock struct(s), heap size 1136, 0 row lock(s), undo log entries 1

MySQL thread id 8, OS thread handle 1358473536, query id 1271 localhost root cleaning up

select sql_text from performance_schema.events_statements_current where THREAD_ID in (select THREAD_ID from performance_schema.threads where PROCESSLIST_ID=8)

或

select b.conn_id,b.thd_id,a.last_statement from sys.session a,sys.processlist b where a.thd_id=b.thd_id and a.conn_id=b.conn_id and b.conn_id=8

查詢鎖源線程

select a.trx_mysql_thread_id,a.* from information_schema.INNODB_TRX a where trx_id in (select blocking_trx_id from information_schema.INNODB_LOCK_WAITS)

查詢被鎖線程

select a.trx_mysql_thread_id,a.* from information_schema.INNODB_TRX a where trx_id in (select requesting_trx_id from information_schema.INNODB_LOCK_WAITS)

查詢XX線程被誰堵塞了select trx_mysql_thread_id blocking_thread,trx_started,trx_query from information_schema.INNODB_TRX where trx_id in

(select blocking_trx_id from information_schema.INNODB_LOCK_WAITS where requesting_trx_id in

(select trx_id from information_schema.INNODB_TRX where trx_mysql_thread_id='XX')

)

5.7.9版本后，建議使用sys.schema_table_lock_waits和sys.innodb_lock_waits來查堵塞，不過需要開啟參數(shù)performance_schema=ON

sys.schema_table_lock_waits

select * from sys.schema_table_lock_waits where object_name=`'test'.'t'`\G

select blocking_pid from sys.schema_table_lock_waits where object_name=`'test'.'t'`\G

https://dev.mysql.com/doc/refman/5.7/en/sys-schema-table-lock-waits.html

sys.innodb_lock_waits

select * from sys.innodb_lock_waits where locked_table=`'test'.'t'`\G

select blocking_pid from sys.innodb_lock_waits where locked_table=`'test'.'t'`\G

https://dev.mysql.com/doc/refman/5.7/en/sys-innodb-lock-waits.html

查詢user1用戶的權(quán)限

show grants for user1

查看所有binary日志

show binary logs;

show master logs;

查看當(dāng)前binary日志文件狀態(tài)

show master status;

刷新binary日志

flush binary logs;

刪除某個(gè)binary日志之前的所有日志

purge binary logs to 'mysql-bin.000003';

刪除所有的binary log

mysql> reset master;

查詢有多少條慢查詢記錄

mysql> show global status like '%Slow_queries%';

執(zhí)行一個(gè)10秒的查詢

mysql> select sleep(10);

查找持續(xù)時(shí)間超過 60s 的事務(wù)

select * from information_schema.innodb_trx where TIME_TO_SEC(timediff(now(),trx_started))>60

查詢所有數(shù)據(jù)庫的數(shù)據(jù)和索引的大小

select round(sum(data_length+index_length)/1024/1024) as total_mb,round(sum(data_length)/1024/1024) as data_mb,round(sum(index_length)/1024/1024) as index_mb from information_schema.tables

查詢每個(gè)數(shù)據(jù)庫的引擎、容量、總表數(shù)

select table_schema,engine,

round(sum(data_length+index_length)/1024/1024) as total_mb,

round(sum(data_length)/1024/1024) as data_mb,

round(sum(index_length)/1024/1024) as index_mb

count(*) as tables

from information_schema.tables

where table_schema not in('INFORMATION_SCHEMA','PERFORMANCE_SCHEMA') group by table_schema,engine order by 3 desc

查詢耗CPU的SQL

mysql> show full processlist;

找到Time最大的，其對應(yīng)的ID列就是耗cpu最厲害的線程ID，對應(yīng)的Info列就是具體的SQL

或

查看慢查詢?nèi)罩?，找到Query_time值最大的行，會(huì)記錄其線程ID號(hào)和具體的SQL

在master上查看有哪些slave

mysql> select * from information_schema.processlist as p where p.command = 'Binlog Dump';

或

mysql> show slave hosts;(此方法需要在從服務(wù)啟動(dòng)時(shí)指定--report-host=HOSTNAME選項(xiàng)，此處HOSTNAME為任意名稱。)

殺線程的SQL，以下兩者必須同時(shí)使用，其中kill thread_id=kill connection thread_id

mysql>kill query thread_id

mysql>kill thread_id

所有數(shù)據(jù)庫事件的查看

select db,name,last_executed,status from mysql.event;

單個(gè)數(shù)據(jù)庫的事件查看

show events from dbname\G;

禁用某個(gè)數(shù)據(jù)庫的某個(gè)事件

alter event dbname.eventname disable;

重新收集表的統(tǒng)計(jì)信息

analyze table tablename

重建表

alter table tablename engine=innodb

修改表的存儲(chǔ)引擎為innodb

alter table tablename engine=innodb

優(yōu)化表

optimize table tablename=analyze table tablename + alter table tablename engine=innodb

修改proc存儲(chǔ)過程的definer，比如把'dev_user@%'改成'prod_user@%'
select db,name,type,definer from mysql.proc\G;
update mysql.proc set definer='prod_user@%' where definer='dev_user@%'

修改event事件的definer，比如把'dev_user@%'改成'prod_user@%'
select db,name,definer from mysql.event\G;
update mysql.event set definer='prod_user@%' where definer='dev_user@%'

本文名稱：mysqldba常用的查詢語句
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