Question

我在使用以下查询时遇到问题：

SELECT 
IFNULL(t4.ItemID, 
IFNULL(t3.ItemID, IFNULL(t2.ItemID, t1.ItemID))) AS ID, 
IFNULL(t4.ParentItemID, 
IFNULL(t3.ParentItemID, 
IFNULL(t2.ParentItemID, t1.ParentItemID))) as Parent, 
IFNULL(tp4.ItemNo, IFNULL(tp3.ItemNo, IFNULL(tp2.ItemNo, tp1.ItemNo))) AS ItemNo
FROM ItemsParents AS t1
LEFT JOIN ItemsDB AS tP1 
ON t1.ItemID = tP1.ID
LEFT JOIN ItemsParents AS t2 
ON t1.ItemID = t2.ParentItemID
LEFT JOIN ItemsDB AS tP2 
ON t2.ItemID = tP2.ID
LEFT JOIN ItemsParents AS t3 
ON t2.ItemID = t3.ParentItemID
LEFT JOIN ItemsDB AS tP3 
ON t3.ItemID = tP3.ID
LEFT JOIN ItemsParents AS t4 
ON t3.ItemID = t4.ParentItemID
LEFT JOIN ItemsDB AS tP4 
ON t4.ItemID = tP4.ID
WHERE t1.ParentItemID = 
(
SELECT ID 
FROM ItemsDB 
WHERE ItemNoInt = 359
)

此表应从选择的第一部分返回两行（822和875），并追加来自ItemsParents LEFT JOINS的更多行。它会附加新行，但原始两行中的一行会丢失   822个
  859个
  834个
  846个
  810个
......所以 875行丢失了 如果我从父项中删除LEFT JOIN "= 1 -- "（SELECT IFNULL ( t4.ItemID, IFNULL(t3.ItemID, IFNULL(t2.ItemID, t1.ItemID))) AS ID, IFNULL(t4.ParentItemID, IFNULL(t3.ParentItemID, IFNULL(t2.ParentItemID, t1.ParentItemID))) as Parent, IFNULL(tp4.ItemNo, IFNULL(tp3.ItemNo, IFNULL(tp2.ItemNo, tp1.ItemNo))) AS ItemNo FROM ItemsParents AS t1 LEFT JOIN ItemsDB AS tP1 ON t1.ItemID = tP1.ID LEFT JOIN ItemsParents AS t2 ON t1.ItemID = 1 -- t2.ParentItemID LEFT JOIN ItemsDB AS tP2 ON t2.ItemID = tP2.ID LEFT JOIN ItemsParents AS t3 ON t2.ItemID = 1 -- t3.ParentItemID LEFT JOIN ItemsDB AS tP3 ON t3.ItemID = tP3.ID LEFT JOIN ItemsParents AS t4 -- t4.ParentItemID ON t3.ItemID = 1 LEFT JOIN ItemsDB AS tP4 ON t4.ItemID = tP4.ID WHERE t1.ParentItemID = ( SELECT ID FROM ItemsDB WHERE ItemNoInt = 359 ) - 评论原始条件）：

{{1}}

...我从左连接表（822和875）返回正确的两行。

我搜索了左连接表中丢失行的情况，但似乎没有一个适用于这种情况。有什么想法吗？

此致

Libor的

Answer 1

不是答案，只是IDEA，我希望您已经要求在左连接中找到最后一行表格，

select LastRowofSubTable.* from tableMain
outer apply
(
    select top 1 * from tableSub
    where tableMain.id = tableSub.id
    order by tableSub.pk_id desc
)as LastRowofSubTable

LEFT JOIN - 从LEFT表选择中丢失一行

1 个答案: