### 查询指定SQL的trace信息 ```sql mysql -uUSER -pPWD -hHOST -e "\ use ins_tc_prd; \ set session optimizer_trace='enabled=on'; \ set optimizer_trace_max_mem_size = 1638400; \ explain SQL; \ select * from information_schema.optimizer_trace\G;" > trace_log.log ``` ### 查询某张表大小 ```sql table_schema = 'testdb_monitor' ORDER BY (data_length + index_length) DESC; ``` ### 查看表空间的使用情况 ```sql select table_name, (data_length+ index_length) /1024/1024 as total_mb, table_rows from information_schema.tables where table_schema= 'Database' ;//不写就是全部 ``` ### MySQL查询阻塞语句 ```sql 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; ``` ### 查询表的数据量大小 ```sql select table_name,(data_length + index_length)/1024/1024 as table_mb,table_rows from information_schema.tables where table_schema='zabbix'; ``` ### 统计数据库中访问量前10的IP ```sql SELECT SUBSTRING_INDEX(host, ':', 1) AS ip, COUNT(*) FROM information_schema.processlist GROUP BY ip ORDER BY COUNT(*) DESC LIMIT 10; ```