MySQL 基础入门_05SQL补充及Information_schema

1. show 语句的列表介绍 ******

查看所有的库

   show databases; 

– 查看当前库下的所有表

   show tables;
   show tables from world;

– 查看当前并发会话信息

show processlist;
show  full processlist;

– 查看数据库支持的权限

show privileges;

– 查看数据库参数信息

show variables 
show variables like '%trx%';

– 查看字符集&校对规则

show  charset;
show  collation;

– 查看建库&建表语句

show create database world;
show create table world.city;

– 查看用户权限

show grants for root@'localhost';

– 查看支持的存储引擎

show engines;

– 查询表中索引信息

show index from world.city;

– 查看数据库当前状态信息

show status;
show status like '%lock%';

– 查看InnoDB引擎相关的状态信息(内存,事务,锁,线程…)

show engine innodb status\G

– 查看二进制日志相关信息

show binary logs ;
show master status; 
show binlog events in 'xxxx';

– 查看主从复制相关信息

show relaylog events in 'xxxx';
show slave status \G

–更多查看帮助

mysql> help show ;

2. Information_schema 统计信息库

• 2.1 介绍:
  视图 :给库数据做别名
  安全 : 只允许查询,不知道操作的是什么对象.
  方便 : 只需要简单的select语句即可使用.
• 2.2 作用:
  方便做数据库资产统计
  库\表 :
  个数
  数据量(大小,行数)
  每张表的数据字典信息
  获取到Server层状态信息
  获取到InnoDB引擎层的状态信息
• 2.3 应用举例:

TABLES :

TABLE_SCHEMA  : 表所在的库 
TABLE_NAME    : 表名
ENGINE        : 表的引擎      
TABLE_ROWS    : 表的行数
AVG_ROW_LENGTH: 平均行长度(字节) 
INDEX_LENGTH  : 索引占用长度(字节) 
TABLE_COMMENT : 表注释 

– 例子:
– 1. 简单查询体验TABLES信息

SELECT * FROM TABLES;

– 2. 所有业务库和表的名字.

SELECT table_schema , table_name 
FROM information_schema.tables
WHERE table_schema NOT IN ('sys','information_schema','performance_schema','mysql');

– 3. 统计每个业务库,表的个数和列表

SELECT table_schema , COUNT(table_name),GROUP_CONCAT(table_name) 
FROM information_schema.tables
WHERE table_schema NOT IN ('sys','information_schema','performance_schema','mysql')
GROUP BY table_schema;

– 4. 统计业务数据库的总数据量

SELECT SUM(table_rows * AVG_ROW_LENGTH+index_length)/1024 AS total_KB
FROM information_schema.tables
WHERE table_schema NOT IN ('sys','information_schema','performance_schema','mysql');

– 5. 每个业务库分别统计数据量

SELECT table_schema,SUM(table_rows * AVG_ROW_LENGTH+index_length)/1024 AS total_KB
FROM information_schema.tables
WHERE table_schema NOT IN ('sys','information_schema','performance_schema','mysql')
GROUP BY table_schema
ORDER  BY total_KB DESC ;

– 6. top 3 数据量大的表

SELECT table_schema,table_name,(table_rows * AVG_ROW_LENGTH+index_length)/1024 AS table_kb
FROM information_schema.tables
WHERE table_schema NOT IN ('sys','information_schema','performance_schema','mysql')
ORDER BY  table_kb DESC 
LIMIT 3;

– 7. 查询所有非INNODB的表

SELECT table_schema,table_name ,ENGINE FROM information_schema.tables
WHERE table_schema NOT IN ('sys','information_schema','performance_schema','mysql')
AND ENGINE <> 'innodb';

– 8. 查询所有非INNODB的表 , 并且提出修改建议

SELECT 
table_schema,
table_name ,
ENGINE ,
CONCAT("alter table ",table_schema,".",table_name," engine=innodb;") AS "修改建议"
FROM information_schema.tables
WHERE table_schema NOT IN ('sys','information_schema','performance_schema','mysql')
AND ENGINE <> 'innodb';

– 9. 所有业务库和表的名字,并且生成备份语句

SELECT 
table_schema , 
table_name ,
CONCAT("mysqldump ",table_schema," ",table_name," > /bak/",table_schema,"_",table_name,".sql") AS "备份"
FROM information_schema.tables
WHERE table_schema NOT IN ('sys','information_schema','performance_schema','mysql');