SQL：现有查询的 WHERE 问题

Question

下面的查询是提取每个 sku 的最大 exdt/seq 字段的记录。问题不是只从 WHERE 语句中提取项目 5343553，而是提取所有 5343553 的日期/序列相同的项目。所以在这种情况下，它会收集 100 多条不同项目的记录，这些记录等于 5343553 的最大日期 7/1，seq 2。

SELECT *  
FROM 
    (SELECT   
         item, cpp, exdt, seq, tv_1 + tf_1 AS tt_1
     FROM         
         dbo.sample123) t 
PIVOT 
    (SUM(tt_1) FOR cpp IN ([M], [LL], [OH] AS pvtc

WHERE     
    (exdt = (SELECT MAX(exdt) AS exdtmax
             FROM dbo.sample123 AS b
             WHERE (LTRIM(item) IN ('5343553'))) 
    AND (seq = (SELECT MAX(seq) AS seqmax
                FROM dbo.sample123 AS b
                WHERE (LTRIM(item) IN ('5343553')))))

所以我想的很简单，我将删除 WHERE，它应该给我所有 sku 及其最大日期/序列。下面反而返回空白，没有数据？

SELECT *  
FROM 
    (SELECT   
         item, cpp, exdt, seq, tv_1 + tf_1 AS tt_1
     FROM dbo.sample123) t 
PIVOT 
    (SUM(tt_1) FOR cpp IN ([M], [LL], [OH] AS pvtc

WHERE     
    (exdt = (SELECT MAX(exdt) AS exdtmax
             FROM dbo.sample123 AS b))
    AND (seq = (SELECT MAX(seq) AS seqmax
                FROM dbo.sample123 AS b))

我不确定我错过了什么。任何帮助将不胜感激！

谢谢。

Answer 1

如果我正确理解了这个问题，并且您的第一个查询的问题是它不是“仅拿起项目 5343553”，那么我建议

WITH mycte AS
(
 SELECT *
 FROM dbo.sample123
 WHERE LTRIM(item) IN ('5343553')
)
SELECT *  
FROM 
    (SELECT   
         item, cpp, exdt, seq, tv_1 + tf_1 AS tt_1
     FROM         
         mycte) t 
PIVOT 
    (SUM(tt_1) FOR cpp IN ([M], [LL], [OH] AS pvtc 
WHERE     
    (exdt = (SELECT MAX(exdt) AS exdtmax
             FROM mycte) 
    AND (seq = (SELECT MAX(seq) AS seqmax
                FROM mycte))

这使您的所有子查询都应用该条件。 （您可以将条件放在所有子查询中，但 CTE 意味着您只需要编写一次。）

根据下面的 cmets，我怀疑您真正想要的是以下内容，它返回所有数据，但仅返回最大值与该项目匹配的行。请注意，我使用LTRIM(t2.item)=LTRIM(t.item)（而不仅仅是t2.item=t.item）与您在WHERE 条件下的操作方式保持一致。

SELECT *  
FROM 
    (SELECT   
         item, cpp, exdt, seq, tv_1 + tf_1 AS tt_1
     FROM         
         dbo.sample123) t 
PIVOT 
    (SUM(tt_1) FOR cpp IN ([M], [LL], [OH] AS pvtc 
WHERE     
    exdt = (SELECT MAX(exdt) AS exdtmax
             FROM dbo.sample123 t2
             WHERE LTRIM(pvtc.item)=LTRIM(t.item)) 
    AND seq = (SELECT MAX(seq) AS seqmax
                FROM dbo.sample123 t2
                WHERE LTRIM(pvtc.item)=LTRIM(t.item))

还有一个可能更简洁的例子：

SELECT *  
FROM 
    (SELECT   
         item, cpp, exdt, seq, tv_1 + tf_1 AS tt_1
     FROM         
         dbo.sample123 t
     WHERE
         exdt = (SELECT MAX(exdt) AS exdtmax
             FROM dbo.sample123 t2
             WHERE LTRIM(t2.item)=LTRIM(t.item)) 
         AND seq = (SELECT MAX(seq) AS seqmax
                FROM dbo.sample123 t2
                WHERE LTRIM(t2.item)=LTRIM(t.item))) t 
PIVOT 
    (SUM(tt_1) FOR cpp IN ([M], [LL], [OH] AS pvtc