面試官：MySQL怎麼查看錶佔用空間大小

前言

在mysql中有一個默認的數據表information_schema，information_schema這張數據表保存了MySQL服務器全部數據庫的信息。如數據庫名，數據庫的表，表欄的數據類型與訪問權限等。

再簡單點，這臺MySQL服務器上，到底有哪些數據庫、各個數據庫有哪些表，每張表的字段類型是什麼，各個數據庫要什麼權限才能訪問，等等信息都保存在information_schema表裏面，因此請勿刪改此表。整理了一份328頁MySQLPDF文檔

代碼

1，切換數據庫

use information_schema;

2，查看數據庫使用大小

select concat(round(sum(data_length/1024/1024),2),’MB’) as data from tables where table_schema=’DB_Name’ ;

3，查看錶使用大小

select concat(round(sum(data_length/1024/1024),2),’MB’) as data from tables where table_schema=’DB_Name’ and table_name=’Table_Name’;

網上找的一個，親測可用:

• 先進去MySQL自帶管理庫：information_schema

• 而後查詢 data_length,index_length

• 你本身的數據庫名：dbname

• 你本身的表名：tablename

  mysql> use information_schema;
  Database changed
  mysql> select data_length,index_length
  -> from tables where
  -> table_schema='dbname'
  -> and table_name = 'tablename';
  +-------------+--------------+
  | data_length | index_length |
  +-------------+--------------+
  | 166379520 | 235782144 |
  +-------------+--------------+
  row in set (0.02 sec)

  mysql> select concat(round(sum(data_length/1024/1024),2),'MB') as data_length_MB,
  -> concat(round(sum(index_length/1024/1024),2),'MB') as index_length_MB
  -> from tables where
  -> table_schema='dbname'
  -> and table_name = 'tablename';
  +----------------+-----------------+
  | data_length_MB | index_length_MB |
  +----------------+-----------------+
  | 158.67MB | 224.86MB |
  +----------------+-----------------+
  row in set (0.03 sec)

  1.查看全部數據庫容量大小

select
table_schema as '數據庫',
sum(table_rows) as '記錄數',
sum(truncate(data_length/1024/1024, 2)) as '數據容量(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.查看全部數據庫各表容量大小

select
table_schema as '數據庫',
table_name as '表名',
table_rows as '記錄數',
truncate(data_length/1024/1024, 2) as '數據容量(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.查看指定數據庫容量大小

例：查看mysql庫容量大小

select
table_schema as '數據庫',
sum(table_rows) as '記錄數',
sum(truncate(data_length/1024/1024, 2)) as '數據容量(MB)',
sum(truncate(index_length/1024/1024, 2)) as '索引容量(MB)'
from information_schema.tables
where table_schema='mysql';

4.查看指定數據庫各表容量大小

例：查看mysql庫各表容量大小

select
table_schema as '數據庫',
table_name as '表名',
table_rows as '記錄數',
truncate(data_length/1024/1024, 2) as '數據容量(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;

select concat(round(sum(data_length/1024/1024),2),'MB') as data_length_MB, concat(round(sum(index_length/1024/1024),2),'MB') as index_length_MB
from tables 
where table_schema='passport' and table_name='tb_user_info';

-- 569.98MB 141.98MB

select concat(round(sum(data_length/1024/1024),2),'MB') as data_length_MB, concat(round(sum(index_length/1024/1024),2),'MB') as index_length_MB
from tables
where table_schema='passport_v2' and table_name='tb_user_info';

-- 2128.94MB 285.00MB 整理了一份328頁MySQLPDF文檔