通過唯一ID和將來最早的日期過濾SQL查詢

Question

我有這個查詢返回正確的數據，但我想過濾它。

SELECT  TOP (100) PERCENT dbo.Reg_Master.id, dbo.Cart_Programs.cartid, dbo.Reg_Master.F_ID, dbo.BlockPeriod.profileid, dbo.Reg_Master.FirstName, 
         dbo.Reg_Master.LastName, dbo.BlockPeriod.startdate, dbo.Cart_Programs.blockid 
FROM   dbo.Cart_Programs LEFT OUTER JOIN 
         dbo.Reg_Master ON dbo.Cart_Programs.cartid = dbo.Reg_Master.cartid LEFT OUTER JOIN 
         dbo.BlockPeriod ON dbo.Cart_Programs.blockid = dbo.BlockPeriod.id 
WHERE  (dbo.BlockPeriod.profileid = xxx) AND (dbo.Reg_Master.F_ID = xxxx) 
ORDER BY dbo.BlockPeriod.startdate 

對於每個dbo.Reg_Master.id，我想只返回最早dbo.BlockPeriod.startdate（即今天或更高版本 - 換句話說，忽略了已經通過日期）每個dbo.Reg_Master.id，我似乎無法得到它正確格式化。

Answer 1

首先，TOP 100 Percent什麼都不做，優化器會忽略它。 此外，您的左連接不起任何作用，因爲您的WHERE條件，所以我編輯了SQL以使用inner join + cross apply vs outer join + outer apply。

如果我對每個Reg_Master記錄正確理解您，您最多隻需要從BlockPeriod獲取1條記錄，其中1條記錄是距離當天日期更近的最近日期。

如果是這樣，那麼你正在尋找的是一個APPLY表操作員TOP (1)組合，如下圖所示：

修訂：

SELECT Reg_Master.id, 
     Cart_Programs.cartid, 
     Reg_Master.F_ID, 
     T.profileid, 
     Reg_Master.FirstName, 
     Reg_Master.LastName, 
     T.startdate, 
     Cart_Programs.blockid 
FROM Cart_Programs 
JOIN Reg_Master ON Cart_Programs.cartid = Reg_Master.cartid 
CROSS APPLY(
    SELECT TOP 1 * FROM BlockPeriod 
    WHERE BlockPeriod.id = Cart_Programs.blockid 
     AND BlockPeriod.profileid = xxx AND Reg_Master.F_ID = xxxx 
     AND BlockPeriod.startdate >= GETDATE() 
ORDER BY BlockPeriod.startdate ASC 
) AS T