mysql - 右连接查询不起作用

Question

我有两个表:opensalesorder 和 items。

我想根据 item_number 从两个表中检索数据，它在下面的查询中工作正常。 (使用内连接)

SELECT opensalesorder.so_number,items.VendorName,opensalesorder.item_number
FROM `opensalesorder` 
INNER JOIN items on opensalesorder.item_number = items.ItemName 
WHERE items.ItemType = 'Stock' and opensalesorder.status NOT LIKE 'on po' 
GROUP BY opensalesorder.item_number

但我也想要“items”表中的所有行，即使没有从 opensalesorder 和 items 中找到 ItemName 的任何匹配项。

但是使用下面的查询似乎对我不起作用。

SELECT opensalesorder.so_number,items.VendorName,opensalesorder.item_number
FROM `opensalesorder` 
RIGHT JOIN items on opensalesorder.item_number = items.ItemName  
WHERE items.ItemType = 'Stock' and opensalesorder.status NOT LIKE 'on po' 
GROUP BY opensalesorder.item_number

即使在左侧没有找到匹配项，右连接也会从右表返回结果。

查询是否正确？

谢谢

Answer 1

这是您的查询:

SELECT opensalesorder.so_number,items.VendorName,opensalesorder.item_number
FROM `opensalesorder` right join
     items
     on opensalesorder.item_number = items.ItemName  
 WHERE items.ItemType = 'Stock' and opensalesorder.status NOT LIKE 'on po'
 group by opensalesorder.item_number;

opensalesorder 上的where 条件是“撤消”右连接。值 NULL 将导致它失败。

解决办法是把它移到on子句中:

SELECT opensalesorder.so_number,items.VendorName,opensalesorder.item_number
FROM `opensalesorder` right join
     items
     on opensalesorder.item_number = items.ItemName and
        opensalesorder.status NOT LIKE 'on po'
 WHERE items.ItemType = 'Stock'
 group by opensalesorder.item_number;