Question

我真的不确定如何解释这个，因为我刚开始尝试以更先进的方式学习如何使用MySQL查询。这就是我所拥有的：

SELECT pa.displayvalue as Brand
FROM product p
JOIN categoryheader ch ON ch.templatetype = 0 AND p.categoryid=ch.categoryid AND ch.isactive=1
JOIN categorydisplayattributes cda ON ch.headerid = cda.headerid AND ch.categoryid = cda.categoryid AND cda.templatetype = ch.templatetype AND cda.isactive=1
JOIN productattribute pa ON p.productid = pa.productid AND cda.attributeid = pa.attributeid AND pa.localeid = 1 AND pa.isactive =1
JOIN attributenames an ON pa.attributeid = an.attributeid AND an.localeid = 1
WHERE p.isactive = 1 AND p.categoryid = 4871
AND an.attributeid = 113319;

所以我有了这个查询，从字面上看，我想做的就是为“And an.attributeid = 113319”添加另一列

我只想添加另一个列而不是113319，我希望它将let的1762的值拉到旁边的列中。

因此，第1列将具有“And an.attributeid = 113319”拉出的所有值，第2列将具有“And an.attributeid = 1762”拉出的所有值。

我得到了这段代码：

SELECT pa.displayvalue as Brand
FROM product p
JOIN categoryheader ch ON ch.templatetype = 0 AND p.categoryid=ch.categoryid AND ch.isactive=1
JOIN categorydisplayattributes cda ON ch.headerid = cda.headerid AND ch.categoryid = cda.categoryid AND cda.templatetype = ch.templatetype AND cda.isactive=1
JOIN productattribute pa ON p.productid = pa.productid AND cda.attributeid = pa.attributeid AND pa.localeid = 1 AND pa.isactive =1
JOIN attributenames an ON pa.attributeid = an.attributeid AND an.localeid = 1
WHERE p.isactive = 1 AND p.categoryid = 4871
AND an.attributeid = 113319;

SELECT pa.displayvalue as Type
FROM product p
JOIN categoryheader ch ON ch.templatetype = 0 AND p.categoryid=ch.categoryid AND ch.isactive=1
JOIN categorydisplayattributes cda ON ch.headerid = cda.headerid AND ch.categoryid = cda.categoryid AND cda.templatetype = ch.templatetype AND cda.isactive=1
JOIN productattribute pa ON p.productid = pa.productid AND cda.attributeid = pa.attributeid AND pa.localeid = 1 AND pa.isactive =1
JOIN attributenames an ON pa.attributeid = an.attributeid AND an.localeid = 1
WHERE p.isactive = 1 AND p.categoryid = 4871
AND an.attributeid = 1762;

但这是在navicat中作为两个单独的结果返回的。我希望这两个结果都是一个结果，而是两列，而不是两个结果，每个结果都有一列。

如您所见，除了最后一行之外，每个选择中的所有行都相同。

我还觉得有一种更好的方法，就是必须使用整个代码两次才能获得an.attributeid的另一列。无论如何，我会拿走我能得到的东西。

如果你有任何建议，我会非常感激。

Answer 1

你可以做这样的事情

... AND an.attributeid IN (113319, 1762 )

这将返回两行，一列。

如果你想将行转换成列，那就更复杂了。

Answer 2

这有时被称为键值存储。你需要玩一些有多个连接的游戏来做你想做的事。

这种事情可以解决问题

SELECT whatever, 
       attr1.displayvalue attr1,
       attr2.displayvalue attr2
  FROM product p
  LEFT JOIN productattribute attr1 ON p.productid = attr1.productid
                                  AND attr1.attributeid = 113319
                                  AND attr1.localeid = 1
                                  AND attr1.isactive = 1
  LEFT JOIN productattribute attr2 ON p.productid = attr2.productid
                                  AND attr2.attributeid = 1762
                                  AND attr2.localeid = 1
                                  AND attr2.isactive = 1

您最终会加入属性表的两个副本，并在连接条件中从每个副本中选择适当的属性ID。您使用左连接而不是普通连接，因此即使缺少该属性，您仍然可以获得该行。

这个数据组织的一个非常常见的例子是WordPress中的wp_postmeta表。

Answer 3

如果您确实想这样做，请进行格式化或报告。这是你要使用的黑客。

使用LEFT JOIN将返回左表中的所有行，右表中的匹配行。当没有匹配时，结果是NULL在右侧。

SELECT p.productid, t2.Type, t1.Brand, t3.Resolution 
FROM product p 
JOIN 
( 
    SELECT p.productid, pa.displayvalue as Brand 
    FROM product p 
    JOIN categoryheader ch ON ch.templatetype = 0 AND p.categoryid=ch.categoryid AND ch.isactive=1 
    JOIN categorydisplayattributes cda ON ch.headerid = cda.headerid AND ch.categoryid = cda.categoryid AND cda.templatetype = ch.templatetype AND cda.isactive=1 
    JOIN productattribute pa ON p.productid = pa.productid AND cda.attributeid = pa.attributeid AND pa.localeid = 1 AND pa.isactive =1 
    JOIN attributenames an ON pa.attributeid = an.attributeid AND an.localeid = 1 
    WHERE p.isactive = 1 AND p.categoryid = 4871 
    AND an.attributeid = 113319 
) t1 ON t1.productid = p.productid 
LEFT OUTER JOIN 
( 
    SELECT p.productid, pa.displayvalue as Type 
    FROM product p 
    JOIN categoryheader ch ON ch.templatetype = 0 AND p.categoryid=ch.categoryid AND ch.isactive=1 
    JOIN categorydisplayattributes cda ON ch.headerid = cda.headerid AND ch.categoryid = cda.categoryid AND cda.templatetype = ch.templatetype AND cda.isactive=1 
    JOIN productattribute pa ON p.productid = pa.productid AND cda.attributeid = pa.attributeid AND pa.localeid = 1 AND pa.isactive =1 
    JOIN attributenames an ON pa.attributeid = an.attributeid AND an.localeid = 1 
    WHERE p.isactive = 1 AND p.categoryid = 4871 
    AND an.attributeid = 1100 
) t2 ON t2.productid = p.productid 
LEFT OUTER JOIN 
( 
    SELECT p.productid, pa.displayvalue as Resolution 
    FROM product p 
    JOIN categoryheader ch ON ch.templatetype = 0 AND p.categoryid=ch.categoryid AND ch.isactive=1 
    JOIN categorydisplayattributes cda ON ch.headerid = cda.headerid AND ch.categoryid = cda.categoryid AND cda.templatetype = ch.templatetype AND cda.isactive=1 
    JOIN productattribute pa ON p.productid = pa.productid AND cda.attributeid = pa.attributeid AND pa.localeid = 1 AND pa.isactive =1 
    JOIN attributenames an ON pa.attributeid = an.attributeid AND an.localeid = 1 
    WHERE p.isactive = 1 AND p.categoryid = 4871 
    AND an.attributeid = 1762 
) t3 ON t3.productid = p.productid

在MySQL中为多个属性添加列

3 个答案: