Question

我的查询如下。

SELECT A.ItemID, A.MSRP, A.SalesPrice, A.Cost, A.DiscountPercent,
       B.QuantityOnHand, B.QuantityAvailable, C.OrderRate, C.OrderQuantity
FROM item_info A
LEFT JOIN inventory_status B
   ON A.ItemID = B.ItemID
LEFT JOIN order_line C
   ON A.ItemID = C.OrderLineItemID
WHERE A.Name LIKE ?
AND C.OrderRate != 0
AND C.OrderQuantity != 0
ORDER BY C.OrderRate ASC, C.OrderQuantity ASC
LIMIT 1

基本上，我们的想法是搜索某个项目并检索其基本信息，库存数量和历史数据。在修改此查询以获取历史数据之前，如果null和QuantityOnHand中的QuantityAvailable和inventory_status都没有null，那么它就能完美地工作order_line 1}}表，而其余的信息将正常返回。但是，尝试加入第三个表不再这样做。现在，没有任何回报。有没有办法修改这个，以便在<script src=".../Scripts/jquery.validate.js"></script> <script src=".../Scripts/jquery.validate.unobtrusive.js"></script>表中没有检索到项目的记录的情况下获得OrderRate和OrderQuantity的def run_query connection.exec_query( "SELECT * FROM TABLE(FN_REQ(#{demo_type_param},#{demo_tid_param}}))") end？

Answer 1

你必须移动谓词

C.OrderRate != 0 AND 
C.OrderQuantity != 0

从WHERE到ON子句：

SELECT A.ItemID, A.MSRP, A.SalesPrice, A.Cost, A.DiscountPercent, 
       B.QuantityOnHand, B.QuantityAvailable, C.OrderRate, C.OrderQuantity
FROM item_info A
LEFT JOIN inventory_status B
   ON A.ItemID = B.ItemID
LEFT JOIN order_line C
   ON A.ItemID = C.OrderLineItemID AND 
      C.OrderRate != 0 AND 
      C.OrderQuantity != 0
WHERE A.Name LIKE ?
ORDER BY C.OrderRate ASC, C.OrderQuantity ASC
LIMIT 1

否则，LEFT JOIN操作将变为INNER JOIN。

Answer 2

更改此部分

LEFT JOIN order_line C
ON A.ItemID = C.OrderLineItemID
WHERE A.Name LIKE ?
AND C.OrderRate != 0
AND C.OrderQuantity != 0

到这个

LEFT JOIN order_line C
ON A.ItemID = C.OrderLineItemID
AND C.OrderRate != 0
AND C.OrderQuantity != 0
WHERE A.Name LIKE ?

SQL - 左连接到两个表不返回任何内容

2 个答案: