Question

我需要为C＃中的特定方法（使用NHibernate）执行原始SQL，并且我很难将查询合并到不同的表中，因为我几乎不使用ORM。在这种情况下，我正在查询其中的三个，我想从第二个查询的最后一行中的第一个简单选择的结果中使用offerId（而不是使用harcoded 1003）

SELECT * FROM [OFFER]
WHERE CampaignId = 1 AND Processed Is NULL

SELECT [BANK].* FROM [BANK]
INNER JOIN [REMINDER]
ON [BANK].personId = [REMINDER].personId AND [BANK].isCurrent = 1
WHERE [REMINDER].offerId = 1003

我尝试过第一个查询，然后使用foreach，但最后我会得到与数据库一样多的查询结果，这样会杀死性能，对吗？

由于

Answer 1

SELECT [BANK].* FROM [BANK]
INNER JOIN [REMINDER]
ON [BANK].personId = [REMINDER].personId AND [BANK].isCurrent = 1
WHERE [REMINDER].offerId in
(
SELECT offerId  FROM [OFFER]
WHERE CampaignId = 1 AND Processed Is NULL
)

Answer 2

使用IN谓词：

SELECT [BANK].* 
FROM [BANK]
INNER JOIN [REMINDER] ON [BANK].personId = [REMINDER].personId 
WHERE [BANK].isCurrent = 1
  AND [REMINDER].offerId IN (SELECT offerId FROM [OFFER]
                             WHERE CampaignId = 1 AND Processed Is NULL)

Answer 3

数据以某种方式相关联。这意味着那里必须有一把外键。你应该去内部加入。

SELECT [BANK].* [OFFER].* FROM [BANK]
INNER JOIN [REMINDER]
  ON [BANK].personId = [REMINDER].personId AND [BANK].isCurrent = 1
INNER JOIN [OFFER]
  ON [REMINDER].offerId = [OFFER].id
WHERE [OFFER].CampaignId = 1 AND [OFFER].Processed Is NULL

这假设[OFFER]中的主键是id。

Answer 4

这是最直接的翻译，在最初的两个查询中可能最容易理解：

SELECT [BANK].* FROM [BANK]
INNER JOIN [REMINDER]
ON [BANK].personId = [REMINDER].personId AND [BANK].isCurrent = 1
WHERE [REMINDER].offerId IN (

  SELECT OfferId FROM [OFFER]
  WHERE CampaignId = 1 AND Processed Is NULL

)

您还可以使用JOIN语法：

SELECT [BANK].*
FROM [BANK]
     JOIN [REMINDER] ON [BANK].personId = [REMINDER].personId
                          AND [BANK].isCurrent = 1
     JOIN [OFFER] ON [REMINDER].OfferId = [OFFER].OfferId
WHERE [OFFER].CampaignId = 1 AND [OFFER].Processed Is NULL

请注意，INNER JOIN和JOIN是等效的语法。

将两个SQL查询合并为一个

4 个答案: