information_schema.tables视图
desc information_schema.TABLES
TABLE_SCHEMA ---->库名
TABLE_NAME ---->表名
ENGINE ---->引擎
TABLE_ROWS ---->表的行数
AVG_ROW_LENGTH ---->表中行的平均行（字节）
INDEX_LENGTH ---->索引的占用空间大小（字节）
查询整个数据库中所有库和所对应的表信息
select table_schema,group_concat(table_name)
from information_schema.tables
group by table_schema;
统计所有库下的表个数
select table_schema,count(table_name)
FROM information_schema.TABLES
GROUP BY table_schema
查询所有innodb引擎的表及所在的库
select table_schema,table_name,ENGINE FROM information_schema.`TABLES`
WHERE engine='innodb';
统计world数据库下每张表的磁盘空间占用
SELECT table_name,CONCAT((TABLE_ROWS*AVG_ROW_LENGTH+INDEX_LENGTH)/1024," KB") AS size_KB
FROM information_schema.tables WHERE TABLE_SCHEMA='world';
统计所有数据库的总的磁盘空间占用
SELECT
TABLE_SCHEMA,
CONCAT(SUM(TABLE_ROWS*AVG_ROW_LENGTH+INDEX_LENGTH)/1024," KB") AS Total_KB
FROM information_schema.tables
GROUP BY table_schema;
mysql -uroot -p123 -e "SELECT TABLE_SCHEMA,CONCAT(SUM(TABLE_ROWS*AVG_ROW_LENGTH+INDEX_LENGTH)/1024,' KB') AS Total_KB FROM information_schema.tables GROUP BY table_schema;"
生成整个数据库下的所有表的单独备份语句
模板语句：
mysqldump -uroot -p123 world city >/tmp/world_city.sql
SELECT CONCAT("mysqldump -uroot -p123 ",table_schema," ",table_name," >/tmp/",table_schema,"_",table_name,".sql" )
FROM information_schema.tables
WHERE table_schema NOT IN('information_schema','performance_schema','sys')
into outfile '/tmp/bak.sh' ;
CONCAT("mysqldump -uroot -p123 ",table_schema," ",table_name," >/tmp/",table_schema,"_",table_name,".sql" )
107张表，都需要执行以下2条语句
ALTER TABLE world.city DISCARD TABLESPACE;
ALTER TABLE world.city IMPORT TABLESPACE;
SELECT CONCAT("alter table ",table_schema,".",table_name," discard tablespace")
FROM information_schema.tables
WHERE table_schema='world'
INTO OUTFILE '/tmp/dis.sql';
show 命令
show databases; #查看所有数据库
show tables; #查看当前库的所有表
show tables from 库名 #查看某个指定库下的表
show create database 库名 #查看建库语句
show create table 库名.表名 #查看建表语句
show grants for root@'localhost' #查看用户的权限信息
show charset； #查看字符集
show collation #查看校对规则
show processlist; #查看数据库连接情况
show index from #表的索引情况
show status #数据库状态查看
SHOW STATUS LIKE '%lock%'; #模糊查询数据库某些状态
SHOW VARIABLES #查看所有配置信息
SHOW variables LIKE '%lock%'; #查看部分配置信息
show engines #查看支持的所有的存储引擎
show engine innodb status\G #查看InnoDB引擎相关的状态信息
show binary logs #列举所有的二进制日志
show master status #查看数据库的日志位置信息
show binlog evnets in #查看二进制日志事件
show slave status \G #查看从库状态
SHOW RELAYLOG EVENTS #查看从库relaylog事件信息
desc (show colums from city) #查看表的列定义信息
http://dev.mysql.com/doc/refman/5.7/en/show.html
