+-----+--------+-----------+--------------+---------+------+----------------------+---------+ | Id | User | Host | db | Command | Time | State | Info …
show full PROCESSLIST; show VARIABLES like 'tmp_table_size' set GLOBAL tmp_table_size=629145600; SHOW VARIABLES LIKE 'max_heap_table_size%'; SET GLOBAL max_heap_table_size=1073741824;…
项目中遇到了慢查询问题 Sql语句 SELECT sum(price) AS price, `member_id` FROM `crm_upload` GROUP BY member_id ORDER BY price DESC LIMIT ; Explain 之后的结果: MariaDB ; +------+-------------+------------+------+---------------+------+---------+------+--------+-----------…
mysql copy表或表数据常用的语句整理汇总. 假如我们有以下这样一个表: id username password ----------------------------------- 1 admin ************* 2 sameer ************* 3 stewart ************* #SQL CREATE TABLE IF NOT EXISTS `admin` ( `id` int(6) unsigned NOT NULL auto_increme…
The easiest way to create a copy of a table is to use a Transact-SQL command. Use SELECT INTO to extract all the rows from an existing table into the new table. The new table must not exist already. The following example will copy the Customers table…
detecting locked tables mysql (locked by LOCK TABLE) up vote15down votefavorite 7 I would like to know whether there is an option to detect locked tables in mysql or not. I mean locked by LOCK TABLE table WRITE/READ command? mysql locking share|impro…
Every derived table must have its own alias 派生表都必须有自己的别名 一般在多表查询时,会出现此错误. 因为,进行嵌套查询的时候子查询出来的的结果是作为一个派生表来进行上一级的查询的,所以子查询的结果必须要有一个别名, 把MySQL语句改成:select count(*) from (select * from ……) as total; 问题就解决,虽然只加了一个没有任何作用的别名total,但这个别名是必须的. select name1 name,…
最近经常遇到mysql数据库死锁,郁闷死, show processlist; 时 Waiting for table metadata lock 能一直锁很久 下面有官网的一段话,可以理解下 http://dev.mysql.com/doc/refman/5.5/en/metadata-locking.html 8.10.4. Metadata Locking MySQL 5.5.3 and up uses metadata locking to manage access to object…
最后参考http://blog.sina.com.cn/s/blog_6942a1590101429h.html 来解决,摘录下核心 后来GOOGLE得知,需要重建该表才可以. 1. 设置新的参数 mysql> set global max_heap_table_size=1048576000 mysql> set global tmp_table_size=1048576000 2. 修改mysql配置文件,使得mysql重新启动时变动能够持续生效. 3. 最后,你需要重新连上MYSQL,重…
1 CREATE TABLE A LIKE B此种方式在将表B复制到A时候会将表B完整的字段结构和索引复制到表A中来. 2. CREATE TABLE A AS SELECT * FROM B 此种方式只会将表B的字段结构复制到表A中来,但不会复制表B中的索引到表A中来.这种方式比较灵活可以在复制原表表结构的同时指定要复制哪些字段,并且自身复制表也可以根据需要增加字段结构. 两种方式在复制表的时候均不会复制权限对表的设置.比如说原本对表B做了权限设置,复制后,表A不具备类似于表B的权…
