EXISTS IN查询如何？

Question

有人可以帮助我，我有2个表

financeaccountcurrencymapping和ownedac​​count。

我想选择那些其字段legalEntity_id是something的financeaccountcurrencymapping。

这是我到目前为止。

SELECT 
FROM financeaccountcurrencymapping 
WHERE ownedAccount_id EXISTS IN (
       SELECT id 
       FROM ownedaccount 
       WHERE legalEntity_id = ??); 

在表中的字段有：

'financeaccountcurrencymapping'

• ID
• moneyCurrency
• accountForCash_id
• ownedAccount_id

'ownedac​​count'

• ID
• 名
• legalEntity_id
• assetOrLiability
• assetType
• depositoryType
• liabilityType
• multipleCurrency
• 货币
• 描述

Answer 1

你不会使用EXISTS在这种情况下。独自一人就可以工作。

SELECT 
FROM financeaccountcurrencymapping 
WHERE ownedAccount_id IN (SELECT id FROM ownedaccount WHERE legalEntity_id = ??); 

Answer 2

SELECT legalEntity_id 
FROM financeaccountcurrencymapping 
WHERE ownedAccount_id IN (
       SELECT id 
       FROM ownedaccount 
       WHERE legalEntity_id = ??); 

Answer 3

你原来的查询是非常接近。你只需要删除EXISTS，像这样：

SELECT * 
FROM financeaccountcurrencymapping 
WHERE ownedAccount_id IN (
       SELECT id 
       FROM ownedaccount 
       WHERE legalEntity_id = ??); 

或者，你可以写这个查询与JOIN对于相同的有效结果。

SELECT f.* 
FROM financeaccountcurrencymapping AS f 
INNER JOIN ownedaccount AS o ON (f.id = o.ownedAccount_id) 
WHERE o.legalEntity_id = ??; 

Answer 4

如果你真的想使用EXISTS或想看看它是如何使用的例子，我认为下面会工作。就我个人而言，我可能会使用IN。

SELECT 
FROM financeaccountcurrencymapping as f 
WHERE EXISTS (SELECT id 
       FROM ownedaccount 
       WHERE f.ownedAccount_id = id AND legalEntity_id = ??);