MYSQL

2023-08-12 07:29| 来源: 网络整理| 查看: 265

假设有张表叫table_name；其中有四个字段

CREATE TABLE `table_name` ( id bigint(20) not null auto_increment, detail varchar(2000), createtime datetime, validity int default '0', primary key (id) );

每个字段设计完成后占用的字节数

bigint 8字节 varchar 2000 字节 datetime 8字节 validity 4字节

算乘法计算占用磁盘：

(8+2000+8+4) * 10000000 = 20200000000 字节 == 18G

此时大概明白，为什么要在设计数据库的时候，采用最小类型的原则了吧

其实该计算公式仅为简单计算；mysql索引和表分离本身是分离，有时索引占用的磁盘空间可能比表占用的磁盘空间都要大！！

参看SQL:

1. 库空间以及索引空间大小:

select TABLE_SCHEMA, concat(truncate(sum(data_length)/1024/1024,2),' MB') as data_size, concat(truncate(sum(index_length)/1024/1024,2),'MB') as index_size from information_schema.tables group by TABLE_SCHEMA order by data_length desc;

2. 查询某个数据库内每张表的大小：

SELECT TABLE_NAME,CONCAT(TRUNCATE(SUM(data_length)/1024/1024,2),' MB') AS data_size, CONCAT(TRUNCATE(index_length/1024/1024,2),' MB') AS index_size FROM information_schema.tables WHERE TABLE_SCHEMA = 'usmschis' GROUP BY TABLE_NAME;

3.查看数据库中所有表的信息

SELECT CONCAT(table_schema,'.',table_name) AS 'Table Name', CONCAT(TRUNCATE(table_rows/1000000,2),'M') AS 'Number of Rows', CONCAT(TRUNCATE(data_length/(1024*1024*1024),2),'G') AS 'Data Size', CONCAT(TRUNCATE(index_length/(1024*1024*1024),2),'G') AS 'Index Size' , CONCAT(TRUNCATE((data_length+index_length)/(1024*1024*1024),2),'G') AS 'Total' FROM information_schema.TABLES WHERE table_schema LIKE 'usmschis';

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