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我有一张桌子，上面有几件商品的价格历史记录——

Item   Date    Price
  X   1Jan13    100
  X   2Jan13    110
 ...
  X   31Dec13   115
  Y   1Jan13     50
  Y   2Jan13     47
 ...
  Y   31Dec13    58

等等。

我刚刚写了一个查询，以找出特定商品的价格连续三天没有变化的日期。使用两个内连接我的查询以以下格式返回输出 -

Item   Date1     Date2     Date3  Price
 X    2Jun13    3Jun13    4Jun13   110
 X    3Jun13    4Jun13    5Jun13   110
 ...
 X    29Dec13   30Dec13   31Dec13  125
 Y    29Mar13   30Mar13   31Mar13  55

现在，我的问题是如何获得以下格式的输出

Item  Date     Price
 X    2Jun13    110
 X    3Jun13    110
 X    4Jun13    110
 X    5Jun13    110
 X    29Dec13   125
 X    30Dec13   125
 X    31Dec13   125

等等所有项目。也就是说，如何组合/合并三个日期字段（不重复）以生成单个日期字段？因为正如你所看到的，与我现在得到的相比，所需的格式更容易阅读。

这是我用于查询的代码：

Select x.* 
From (
      Select T1.ItemName As Item, T1.Date As Date_3, T2.Date As Date_2, T3.Date As Date_1,
      Round((T1.Price - T2.Price), 2) As Change, Round((T1.Price - T3.Price), 2) As Change_2, T1.Price As Price
      From MarketData As T1 Inner Join MarketData As T2 On T1.ItemName = T2.ItemName 
      Inner Join MarketData As T3 On T2.ItemName = T3.ItemName
      Where (T1.Date = T3.Date + 2 Or (DatePart(DW, T3.Date) In (5, 6) And T1.Date = T3.Date + 4)) And 
     (T2.Date = T3.Date + 1 Or (DatePart(DW, T3.Date) = 6 And T2.Date = T3.Date + 3))
 ) As x
Where x.Change = 0 And x.Change_2 = 0

任何帮助深表感谢。

4

1 回答 1

1

如果您的数据库支持联合，您可以这样做：

select Item, Date, Price from
(
select Item, Date1 as Date, Price from (<1st select here>) res
union
select Item, Date2 as Date, Price from (<1st select here>) res
union
select Item, Date3 as Date, Price from (<1st select here>) res
) table
order by Date

您还可以在子查询中转换 <1st select here> 并进一步优化 sql。

编辑：这里包含您的查询，我显然没有尝试过，但希望它会有所帮助:)

select table.Item, table.Date, table.Price from
(
select Item, Date1 as Date, Price from tdp res
union
select Item, Date2 as Date, Price from tdp res
union
select Item, Date3 as Date, Price from tdp res
) table,
(Select x.* 
From (
      Select T1.ItemName As Item, T1.Date As Date_3, T2.Date As Date_2, T3.Date As Date_1,
      Round((T1.Price - T2.Price), 2) As Change, Round((T1.Price - T3.Price), 2) As Change_2, T1.Price As Price
      From MarketData As T1 Inner Join MarketData As T2 On T1.ItemName = T2.ItemName 
      Inner Join MarketData As T3 On T2.ItemName = T3.ItemName
      Where (T1.Date = T3.Date + 2 Or (DatePart(DW, T3.Date) In (5, 6) And T1.Date = T3.Date + 4)) And 
     (T2.Date = T3.Date + 1 Or (DatePart(DW, T3.Date) = 6 And T2.Date = T3.Date + 3))
 ) As x
Where x.Change = 0 And x.Change_2 = 0) as tdp
order by Date
于 2013-11-04T13:14:35.613 回答