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我希望你能帮助我。我刚开始学习 SQL，在工作中应用我的知识时，我陷入了困境。

我有带有多个表的 SQL 数据库，其中包含待售物品属性的各种数据。到目前为止，我成功地创建了一个查询，它提取了大部分所需的信息。不幸的是，最后一张桌子对我来说成了问题。

表格的格式如下：

| fkStockItemId  | PropertyName | PropertyValue | PropertyType |
|   ItemSKU-1    |  Item Style  |   SB-01123    |   Attribute  |
|   ItemSKU-1    |  Item Size   |    X-Small    |   Attribute  |
|   ItemSKU-1    |  Item Color  |      Red      |   Attribute  |
|   ItemSKU-2    |  Item Style  |   AA-66002    |   Attribute  |
|   ItemSKU-2    |  Item Size   |    Medium     |   Attribute  |
|   ItemSKU-2    |  Item Color  |     Green     |   Attribute  |                            
|   ItemSKU-3    |  Item Style  |    110445     |   Attribute  |
|   ItemSKU-3    |  Item Size   |     Small     |   Attribute  |

我试图得到的输出是这样的：

    |    SKU    |  Item Style  |  Item Size  | Item Color  | 
    | ItemSKU-1 |   SB-01123   |   X-Small   |    Red      |
    | ItemSKU-2 |   AA-66002   |   Medium    |    Green    |
    | ItemSKU-3 |    110445    |    Small    |   *Null*    | 


    Please note that last column "PropertyType" is for technical purposes and 
is not needed to be queried.

这是我到目前为止得到的：

SELECT si.ItemNumber, si.ItemTitle, si.ItemDescription, si.RetailPrice, si.Weight, sl.Quantity, c.CategoryName, siep.ProperyValue, siep.ProperyName
FROM StockItem si
LEFT OUTER JOIN StockLevel sl ON si.pkStockItemID = sl.fkStockItemId
LEFT OUTER JOIN ProductCategories c ON si.CategoryId = c.CategoryId
LEFT OUTER JOIN StockItem_ExtendedProperties siep ON si.pkStockItemID = siep.fkStockItemId
WHERE siep.ProperyName = 'Item Style'

表“StockLevel”和“ProductCategories”显示结果很好。如果您注意到，最后“StockItem_ExtendedProperties”JOIN 和“siep.ProperyValue”、“siep.ProperyName”加上“WHERE siep.ProperyName = 'Item Style'”只允许我查询 1 个属性。感谢您的帮助和时间！

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3 回答 3

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将 propertyname 过滤器从 WHERE 子句移至 ON 子句。然后为每个属性再次加入：

SELECT si.ItemNumber, si.ItemTitle, si.ItemDescription, si.RetailPrice, si.Weight, sl.Quantity, c.CategoryName, style.ProperyValue as style, size.ProperyValue as size
FROM StockItem si
LEFT OUTER JOIN StockLevel sl ON si.pkStockItemID = sl.fkStockItemId
LEFT OUTER JOIN ProductCategories c ON si.CategoryId = c.CategoryId
LEFT OUTER JOIN StockItem_ExtendedProperties style ON si.pkStockItemID = style.fkStockItemId
AND style.ProperyName = 'Item Style'
LEFT OUTER JOIN StockItem_ExtendedProperties size ON si.pkStockItemID = size.fkStockItemId
AND size.ProperyName = 'Item Size'
于 2015-06-23T19:29:18.083 回答
0

要像这样获取列中的每个值，您可以首先为每个属性编写一个子查询，然后将JOIN它们全部放在一起，如下所示：

SELECT m1.fkStockItemId, m1.propertyValue AS 'Item Style', m2.propertyValue AS 'Item Size', m3.propertyValue AS 'Item Color'
FROM(
  SELECT fkStockItemId, propertyValue
  FROM myTable
  WHERE propertyName = 'Item Style') m1
LEFT JOIN(
  SELECT fkStockItemId, propertyValue
  FROM myTable
  WHERE propertyName = 'Item Size') m2 ON m2.fkStockItemId = m1.fkStockItemId
LEFT JOIN(
  SELECT fkStockItemId, propertyValue
  FROM myTable
  WHERE propertyName = 'Item Color') m3 ON m3.fkStockItemId = m2.fkStockItemId;

这是一个SQL Fiddle示例。

于 2015-06-23T19:40:58.213 回答
0

我相信最好的方法是创建一个函数，该函数将返回您需要的属性值以及您在查询中包含的内容。

CREATE FUNCTION dbo.GetItemProperty
(
    @ItemName AS VARCHAR(50)
    , @Property AS VARCHAR(8)
)
RETURNS VARCHAR(50)
AS
BEGIN

    DECLARE @Ans AS VARCHAR(50) = ''

    SELECT  @Ans = PropertyValue 
    FROM    StockItem AS si
    JOIN    StockItem_ExtendedProperties AS siep 
            ON si.pkStockItemID = siep.fkStockItemId
    WHERE   si.pkStockItemID = @ItemName
            AND siep.ProperyName = @Property

    RETURN @Ans;

END
GO

SELECT  si.ItemNumber, 
        si.ItemTitle, 
        si.ItemDescription, 
        si.RetailPrice, 
        si.Weight, 
        sl.Quantity, 
        c.CategoryName, 
        dbo.GetItemProperty(si.pkStockItemID, 'Item Style') AS 'Item Style', 
        dbo.GetItemProperty(si.pkStockItemID, 'Item Size') AS 'Item Size', 
        dbo.GetItemProperty(si.pkStockItemID, 'Item Color') AS 'Item Color'
FROM StockItem si
LEFT OUTER JOIN StockLevel sl 
    ON si.pkStockItemID = sl.fkStockItemId
LEFT OUTER JOIN ProductCategories c 
    ON si.CategoryId = c.CategoryId
LEFT OUTER JOIN StockItem_ExtendedProperties siep 
    ON si.pkStockItemID = siep.fkStockItemId;

祝你好运！

于 2015-06-23T20:01:35.993 回答