Sql 从表A中选择，但排除表B中存在匹配项的位置

我有两个表，订阅者和发送日志。我需要在Sendlog表中选择所有订阅服务器，但排除符合我的条件的记录

标准是他们是“超级用户”，SubscribePreference=1，并且从未收到过“GoPro”电子邮件

我在这里有一个SQL FIDLE来表示它，但无法理解查询

在这个示例中，我想返回Dave，Ed&Frank，因为他们从未收到过“GoPro”电子邮件

有人能帮我吗？

这应该可以：

SELECT DISTINCT s.EmailAddress
   , 'GoPro' AS CampaignName
  , sl.SendDate
FROM Subscribers s 
LEFT JOIN SendLog sl 
  ON s.EmailAddress = sl.EmailAddress
  AND CampaignName = 'GoPro'
WHERE s.Entitlement = 'PowerUser' 
AND s.SubscribePreference = 1
AND sl.EmailAddress IS NULL

这应该可以：

SELECT DISTINCT s.EmailAddress
   , 'GoPro' AS CampaignName
  , sl.SendDate
FROM Subscribers s 
LEFT JOIN SendLog sl 
  ON s.EmailAddress = sl.EmailAddress
  AND CampaignName = 'GoPro'
WHERE s.Entitlement = 'PowerUser' 
AND s.SubscribePreference = 1
AND sl.EmailAddress IS NULL

---

我相信这会奏效：

SELECT DISTINCT Subscribers.EmailAddress
FROM   Subscribers
LEFT OUTER JOIN SendLog
       ON Subscribers.EmailAddress = SendLog.EmailAddress
       AND SendLog.CampaignName = 'GoPro'
WHERE  SendLog.EmailAddress IS NULL
       AND Subscribers.SubscribePreference = 1
       And Subscribers.Entitlement = 'PowerUser'

---

出于性能原因，我建议在Subscribers表中添加一个ID列作为主键，然后在SendLog表中创建一个名为SubscriberID的外键，并在该外键上加入它们。上面的查询可以工作，但使用整数和适当的键会更快。

我相信这会工作：

SELECT DISTINCT Subscribers.EmailAddress
FROM   Subscribers
LEFT OUTER JOIN SendLog
       ON Subscribers.EmailAddress = SendLog.EmailAddress
       AND SendLog.CampaignName = 'GoPro'
WHERE  SendLog.EmailAddress IS NULL
       AND Subscribers.SubscribePreference = 1
       And Subscribers.Entitlement = 'PowerUser'

出于性能原因，我建议在Subscribers表中添加一个ID列作为主键，然后在SendLog表中创建一个名为SubscriberID的外键，并在该外键上加入它们。上面的查询可以工作，但是使用整数和适当的键会更快