性能的嵌套選擇從多個表

我有來自多個表的多個嵌套的選擇查詢，如下所示：性能的嵌套選擇從多個表

select c.name,c.created_date, 
( select count(id) from user u 
    where u.company_id=c.id) as users, 
( select count(distinct uls.user_id) from user_login_status uls 
    where uls.company_id=c.id 
    and uls.date between '2013-11-18' and '2014-01-10') as unique_logins, 
( select count(id) from cash_receiving cr 
    where cr.company_id=c.id 
    and cr.created_date between '2013-11-18' and '2014-01-10') as recognitions, 
0 as licences, 
( select count(id) from inventory_item i 
    where i.company_gid=c.id) as store_items, 
( select count(id) from award a 
    where a.company_gid=c.id) as awards, 
( select uls2.date from user_login_status uls2 
    where uls2.company_id=c.id 
    ORDER BY uls2.date DESC LIMIT 1) as last_login, 
c.id as id, 
c.is_live as live 
from company c 
order by c.name

的user_login_status包含每個用戶的登錄條目，所以將有大量的數據，也就是在SQL我對上面的查詢調用了實體管理器，因此我想知道上述查詢的性能，它是否適合每個表的海量數據，或者更好地做出單獨的select語句，請告知如何使上述查詢執行得很好，謝謝。

來源

2014-01-11 Mahmoud Saleh

你無法測試性能？你所能得到的只是對戰爭故事的猜測和隨機複述。 –

@Marko Topolnik，我的數據庫中沒有龐大的數據，所以我問這是否會在未來造成不好的表現？ –

通過插入大數據來測試它，沒有其他方法知道。 –

試試這個：

SELECT c.name,c.created_date, u.users, uls.unique_logins, cr.recognitions, 
     0 AS licences, i.store_items, s.awards, uls2.last_login, 
     c.id AS id, c.is_live AS live 
FROM company c 
LEFT JOIN (SELECT u.company_id, COUNT(u.id) users 
      FROM user u 
      GROUP BY u.company_id 
     ) AS u ON u.company_id = c.id 
LEFT JOIN (SELECT uls.company_id, COUNT(DISTINCT uls.user_id) unique_logins 
      FROM user_login_status uls WHERE uls.date BETWEEN '2013-11-18' AND '2014-01-10' 
      GROUP BY uls.company_id 
     ) AS uls ON uls.company_id=c.id 
LEFT JOIN (SELECT cr.company_id, COUNT(cr.id) recognitions FROM cash_receiving cr 
      WHERE cr.created_date BETWEEN '2013-11-18' AND '2014-01-10' 
      GROUP BY cr.company_id 
     ) AS cr ON cr.company_id = c.id 
LEFT JOIN (SELECT i.company_gid, COUNT(i.id) store_items 
      FROM inventory_item i 
      GROUP BY i.company_gid 
     ) AS i ON i.company_gid = c.id 
LEFT JOIN (SELECT a.company_gid, COUNT(a.id) awards 
      FROM award a 
      GROUP BY a.company_gid 
     ) AS a ON a.company_gid = c.id 
LEFT JOIN (SELECT uls2.company_id, MAX(uls2.date) last_login 
      FROM user_login_status uls2 
      GROUP BY uls2.company_id 
     ) AS uls2 ON uls2.company_id=c.id 
ORDER BY c.name

來源

2014-01-11 09:18:26

性能的嵌套選擇從多個表

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