Question

我有这个sql select语句：

Select ORDERS.ptDate as Date,Products.Description as Product, 
            ORDERDETAILS2.Quantity   FROM         ORDERS inner join ORDERDetails2 on Orders._id=ORDERDetails2.PtOrder inner join Products on Orderdetails2.ptproduct=Products.PtUnique order by date

对这种数据进行了反复推理：

2014-03-19 00:00:00;"Product a";"4"
2014-03-19 00:00:00;"Product c";"750"
2014-03-19 00:00:00;"Product a";"1"
2014-03-19 00:00:00;"Product b";"1"
2014-03-19 00:00:00;"Product c";"1075"
2014-03-20 00:00:00;"Product b";"2"
2014-03-20 00:00:00;"Product b";"1"
2014-03-20 00:00:00;"Product a";"2"
2014-03-20 00:00:00;"Product c";"2"
2014-03-20 00:00:00;"Product b";"25"

我可以重现这个日期为列，第二列为行，第三列为sqlite中的aggegate函数吗？结果应该是这样的：

Product      2014-03-19    2014-03-20
Product a        5              2
Product b        1              28
Product c      1825             2

感谢您的帮助

Answer 1

您必须进行动态查询，即必须为每个日期生成SQL代码。

首先，获取日期：

SELECT DISTINCT ptDate
FROM Orders
ORDER BY ptDate

然后，从为每个所需产品返回一个记录的查询开始：

SELECT Description AS Product
FROM Products

（如果您想将此限制为某些特定订单中的产品，则必须在此处进行加入，或使用WHERE PtUnique IN (...)。）

然后编写一个查询，将这些产品与每个日期的一列组合在一起。必须使用相关子查询计算这些值：

SELECT Description AS Product,
       (SELECT SUM(OrderDetails2.Quantity)
        FROM OrderDetails2
        JOIN Orders ON OrderDetails2.PtOrder = Orders._id
        WHERE Orders.ptDate = '2014-03-19'
          AND OrderDetails2.PtProduct = Products.PtUnique
       ) AS "2014-03-19",
       (SELECT SUM(OrderDetails2.Quantity)
        FROM OrderDetails2
        JOIN Orders ON OrderDetails2.PtOrder = Orders._id
        WHERE Orders.ptDate = '2014-03-20'
          AND OrderDetails2.PtProduct = Products.PtUnique
       ) AS "2014-03-20"
FROM Products

将行作为sqlite中的数据透视表中的列

1 个答案: