sql查询以获取不同人的最早日期

Question

我试图从表中选择用户可以在3个地方中的最早日期。

SELECT RecordID,  
    (
        SELECT MIN(dDate) 
        FROM (
            VALUES(DateSent), 
            (DiaryDate),                 
            (CareDate)
        ) As EarliestDate(dDate)
    ) AS dDate 
FROM tblOrderDetails 
WHERE Flagged = 0 
AND SalesID= '" & UserID & "'
OR Flagged = 0 
And RepID= '" & UserID & "' 
OR Flagged = 0 
AND CareID= '" & UserID & "'"

Answer 1

如果想要最早的日期，则需要MIN() 。 以下内容将在某些数据库中运行：

SELECT od.RecordID,  
       (SELECT MIN(EarliestDate.dDate) 
        FROM (VALUES (od.DateSent), (od.DiaryDate), (od.CareDate)
             ) As EarliestDate(dDate)
       ) as dDate 
FROM tblOrderDetails od 
WHERE (od.Flagged = 0 AND od.SalesID = '" & UserID & "') OR
      (od.Flagged = 0 AND od.RepID= '" & UserID & "') OR 
      (od.Flagged = 0 AND od.CareID= '" & UserID & "'");

（假设这是您想要的逻辑，则查询中不需要括号。）

WHERE子句可以简化为：

WHERE od.Flagged = 0 AND ? IN (od.SalesId, od.RepId, od.CareId)

注意? 是参数的占位符。 您应该将值作为参数传递，而不要浪费查询字符串。

编辑：

正如Noxtrhon建议的那样，这通常是使用CASE编写的。 最简单的版本（假设没有NULL值）将是：

SELECT od.RecordID, 
       (CASE WHEN od.DateSent <= od.DiaryDate and od.DateSent <= od.CareDate
             THEN ad.DateSent
             WHEN od.DiaryDate <= od.CareDate
             THEN od.DiaryDate
             ELSE od.CareDate
        END) as dDate 
FROM tblOrderDetails od 
WHERE (od.Flagged = 0 AND od.SalesID = '" & UserID & "') OR
      (od.Flagged = 0 AND od.RepID= '" & UserID & "') OR 
      (od.Flagged = 0 AND od.CareID= '" & UserID & "'");

如果我没记错的话， CASE性能应该会稍微好一些，但是改进远不及我预期。

Answer 2

我想我知道您正在尝试做什么。 如果我理解正确，则需要给定RecordID的那三列的最小日期。 您可以通过对每个列的每个RecordID进行UNION ALL来实现。 可以对其进行子查询以获取MIN（date）。 正如Justinas指出的那样，您的WHERE出现了问题，必须小心混合AND和OR。

SELECT dT.RecordID, MIN(dT.inDate) AS [EarliestDate]
  FROM (
          SELECT RecordID, DateSent AS [inDate]
            FROM tblOrderDetails
           WHERE Flagged = 0 
             AND (   SalesID= '" & UserID & "'
                  OR   RepID= '" & UserID & "' 
                  OR  CareID= '" & UserID & "'
                 )

          UNION ALL

          SELECT RecordID, DiaryDate AS [inDate]
            FROM tblOrderDetails
           WHERE Flagged = 0 
             AND (   SalesID= '" & UserID & "'
                  OR   RepID= '" & UserID & "' 
                  OR  CareID= '" & UserID & "'
                 )

          UNION ALL

          SELECT RecordID, CareDate AS [inDate]
            FROM tblOrderDetails
           WHERE Flagged = 0 
             AND (   SalesID= '" & UserID & "'
                  OR   RepID= '" & UserID & "' 
                  OR  CareID= '" & UserID & "'
                 )
       ) AS dT
GROUP BY RecordID

Answer 3

您可以使用案例陈述来检查案例并决定选择哪个案例。 您要求最早的日期，但是您在查询中选择了最晚日期作为Max（...），此查询返回最早的日期：

SELECT RecordID, 
 case when DateSent < DiaryDate and DateSent < CareDate then DateSend
      when DiaryDate < DateSent and DiaryDate < CareDate then DiaryDate
      else CareDate end as dDate
FROM tblOrderDetails
WHERE Flagged = 0 AND
      SalesID = '" & UserID & "'OR Flagged = 0 And
      RepID = '" & UserID & "' OR Flagged = 0 AND CareID= '" & UserID & "'"