Question

我有这样的表：

StartDate  Day1Hours Day2Hours Day3Hours Day4Hours Day5Hours Day6Hours Day7Hours
1/17/2010     8          8          8        8          8         8         8      
1/24/2010     8          8          0        0          10        2         2

如何在2010年1月18日至2010年1月22日之间获取小时数。

Answer 1

使用CROSS JOIN每天多行到一行，并为该行留出适当的小时数。

;WITH cteFixedSchema AS
(
   SELECT
      DATEADD(day, DayOffset, StartDate) AS ProperDate,
      CASE DayOffset
         WHEN 0 THEN Day1Hours
         WHEN 1 THEN Day2Hours
         WHEN 2 THEN Day3Hours
         WHEN 3 THEN Day4Hours
         WHEN 4 THEN Day5Hours
         WHEN 5 THEN Day6Hours
         WHEN 6 THEN Day7Hours
      END AS DayHours
   FROM
      MyTable M
      CROSS JOIN
      (SELECT 0 AS DayOffset UNION SELECT 1 UNION SELECT 2
         UNION SELECT 3 UNION SELECT 4 UNION SELECT 5 UNION SELECT 6) foo
)
SELECT
    SUM(DayHours)
FROM
    cteFixedSchema
WHERE
    ProperDate BETWEEN '20110118' AND '20110122'

这假设StartDate是一个有效的日期（时间）数据类型，不需要额外的转换

Answer 2

使用map int-＆gt; String，它将日期编号映射到列名。

C＃示例：

public class Example
{
    private static Dictionary<int, string> columns;

    static Example()
    {
        columns.Add(1, "Day1Hours");
        columns.Add(2, "Day2Hours");
        columns.Add(3, "Day3Hours");
        columns.Add(4, "Day4Hours");
        columns.Add(5, "Day5Hours");
        columns.Add(6, "Day6Hours");
        columns.Add(7, "Day7Hours");
    }

    public void queryThirdDay(string startDate)
    {
        StringBuilder query = new StringBuilder("SELECT ");
        query.Append(columns[3]); // get third day
        query.Append(" FROM table WHERE StartDate = '");
        query.Append(startDate);
        query.Append("'");

        // query it
        // ...
    }
}

Answer 3

我同意有关架构的评论。如果由于某种原因这不受您的控制，您可以unpivot将其纳入此架构，然后从中进行选择。

Declare @basedata table
(
StartDate datetime,
Day1Hours int,
Day2Hours int,
Day3Hours int,
Day4Hours int,
Day5Hours int,
Day6Hours int,
Day7Hours int
)
INSERT INTO @basedata
select '20100117',8,8,8,8,8,8,8 union all
select '20100124',8,8,0,0,10,2,2

DECLARE @Start DATETIME
DECLARE @End DATETIME

SET @Start = '20100118'
SET @End = '20100122'

SELECT DATEADD(DAY, SUBSTRING(d, 4, 1) - 1, StartDate),
       Hours
FROM   (SELECT *
        FROM   @basedata b
        WHERE  b.StartDate BETWEEN DATEADD(DAY, -7, @Start) AND
                                   DATEADD(DAY, 7, @End))
       filtered UNPIVOT (Hours FOR d IN 
    (Day1Hours, Day2Hours, Day3Hours, Day4Hours, Day5Hours, Day6Hours, Day7Hours) ) AS unpvt
WHERE  DATEADD(DAY, SUBSTRING(d, 4, 1) - 1, StartDate) BETWEEN @Start AND @End

使用列号而不是列名选择查询

3 个答案: