查询数据库大小 查询所有数据库的总大小查询数据库大小：use information_schema; select concat(round(sum(DATA_LENGTH/1024/1024),2),'MB') as data from TABLES;统计一下所有库数据量 每张表数据量=AVG_ROW_LENGTH*TABLE_ROWS+INDEX_LENGTHSELECT SUM(AVG_ROW_LENGTH*TABLE_ROWS+INDEX_LENGTH)/1024/1024 AS total_mb FROM information_schema.TABLES 统计每个库大小：SELECT table_schema,SUM(AVG_ROW_LENGTH*TABLE_ROWS+INDEX_LENGTH)/1024/1024 AS total_mb FROM information_schema.TABLES group by table_schema; 查看指定数据库的大小use information_schema; select concat(round(sum(DATA_LENGTH/1024/1024),2),'MB') as data from TABLES where table_schema='test';1.查看所有数据库各容量大小select table_schema as '数据库', sum(table_rows) as '记录数', sum(truncate(data_length/1024/1024, 2)) as '数据容量(MB)', sum(truncate(index_length/1024/1024, 2)) as '索引容量(MB)' from information_schema.tables group by table_schema order by sum(data_length) desc, sum(index_length) desc;2.查看所有数据库各表容量大小select table_schema as '数据库', table_name as '表名', table_rows as '记录数', truncate(data_length/1024/1024, 2) as '数据容量(MB)', truncate(index_length/1024/1024, 2) as '索引容量(MB)' from information_schema.tables order by data_length desc, index_length desc;3.查看指定数据库容量大小例：查看mysql库容量大小select table_schema as '数据库', sum(table_rows) as '记录数', sum(truncate(data_length/1024/1024, 2)) as '数据容量(MB)', sum(truncate(index_length/1024/1024, 2)) as '索引容量(MB)' from information_schema.tables where table_schema='mysql';　4.查看指定数据库各表容量大小例：查看mysql库各表容量大小select table_schema as '数据库', table_name as '表名', table_rows as '记录数', truncate(data_length/1024/1024, 2) as '数据容量(MB)', truncate(index_length/1024/1024, 2) as '索引容量(MB)' from information_schema.tables where table_schema='mysql' order by data_length desc, index_length desc;

Msql压缩备份及还原 gzip 备份mysqldump -hhostname -uusername -ppassword databasename | gzip > 数据库名称-`date +%Y-%m-%d`.sql.gz还原gunzip < 数据库名称-2020-07-06.sql.gz | mysql -uroot -proot 数据库名称

mysqldump备份及还原(gzip压缩) 备份mysqldump -hhostname -uusername -ppassword databasename | gzip > databasename`date +%Y%m%d`.sql.gz还原gunzip < databasename20200410.sql.gz | mysql -uroot -proot databasename

设置max_connections无效 在/etc/mysql/my.cnf中设置max_connections=512进入Mysql查看发现还是214mysql> show global variables like '%max_connecti%'; +-----------------+-------+ | Variable_name | Value | +-----------------+-------+ | max_connections | 214 | +-----------------+-------+ 1 row in set (0.01 sec)google了一番后，说是跟open_files_limit有关,每个connect都会打开几个文件,查了下open_files_limit为1024。mysql> show global variables like '%open_files_limit%'; +------------------+-------+ | Variable_name | Value | +------------------+-------+ | open_files_limit | 1024 | +------------------+-------+ 1 row in set (0.00 sec)在/etc/mysql/my.cnf中加上open_files_limit = 4096重启mysql后查看mysql> show global variables like '%max_connecti%'; +-----------------+-------+ | Variable_name | Value | +-----------------+-------+ | max_connections | 512 | +-----------------+-------+ 1 row in set (0.01 sec)mysql> show global variables like '%open_files_limit%'; +------------------+-------+ | Variable_name | Value | +------------------+-------+ | open_files_limit | 4096 | +------------------+-------+ 1 row in set (0.00 sec)open_files_limit最大值也是有限制的，设置太大也会变成默认1024，可以在/etc/security/limits.conf加上并重启系统* soft nofile 65536 * hard nofile 65536还有就是启动mysql的service加上LimitNOFILE=65535并重启mysql，这样可以解除open file的限制，LimitNOFILE=65535