按低于某个值的所有日期降序排序，然后按高于该值的所有日期升序排序

Question

给定以下数据：

Effective Date
--------------
    2014-01-01
    2015-01-01
    2016-01-01
    2017-01-01
    2018-01-01

我想按相对于（例如）2016-06-01 的日期排序，其中所有低于2016-06-01 的降序值都位于高于2016-06-01 的所有升序值之前。

Relative to date: 2016-06-01 the desired ordering is

Effective Date
--------------
    2016-01-01
    2015-01-01
    2014-01-01
    2017-01-01
    2018-01-01

我想出的实现所需排序的最佳方法是：

CREATE TABLE #Dates
(
    EffectiveDate DATETIME2
);

DECLARE @CurrentDate DATETIME2 = '2016-06-01';
DECLARE @MinDate DATETIME2 = '0001-01-01';

INSERT INTO #Dates (EffectiveDate) VALUES ('2014-01-01');
INSERT INTO #Dates (EffectiveDate) VALUES ('2015-01-01');
INSERT INTO #Dates (EffectiveDate) VALUES ('2016-01-01');
INSERT INTO #Dates (EffectiveDate) VALUES ('2017-01-01');
INSERT INTO #Dates (EffectiveDate) VALUES ('2018-01-01');

SELECT
    *
FROM
    #Dates
ORDER BY
    CASE
        WHEN #Dates.EffectiveDate < @CurrentDate
            THEN DATEDIFF(DAY, #Dates.EffectiveDate, @CurrentDate)
        ELSE
            DATEDIFF(DAY, @CurrentDate, #Dates.EffectiveDate) - DATEDIFF(DAY, @CurrentDate, @MinDate)
    END;

DROP TABLE #Dates;

有没有更好的方法来实现所需的排序？

Answer 1

如果您有 2012 年及以上版本。

SELECT
    *
FROM
    #Dates
ORDER BY
    IIF(#Dates.EffectiveDate <= @CurrentDate, 0,1) ASC
    , ABS(DATEDIFF(day,#Dates.EffectiveDate, @CurrentDate)) ASC;

如果你有 2008 年：

SELECT
    *
FROM
    #Dates
ORDER BY
    CASE 
        WHEN #Dates.EffectiveDate <= @CurrentDate THEN  0
        ELSE 1 END ASC
    , ABS(DATEDIFF(day,#Dates.EffectiveDate, @CurrentDate)) ASC;

Answer 2

这是一种不同的方法。让我知道这是否适合您的需求。我使用的是表变量而不是临时表。

DECLARE @Dates TABLE
(
 EffectiveDate DATETIME2
);

DECLARE @CurrentDate DATETIME2 = '2016-06-01';

INSERT INTO @Dates (EffectiveDate) VALUES ('2014-01-01');
INSERT INTO @Dates (EffectiveDate) VALUES ('2015-01-01');
INSERT INTO @Dates (EffectiveDate) VALUES ('2016-01-01');
INSERT INTO @Dates (EffectiveDate) VALUES ('2017-01-01');
INSERT INTO @Dates (EffectiveDate) VALUES ('2018-01-01');

SELECT *
FROM (SELECT TOP 1000000 *
    FROM @Dates t1
    WHERE EffectiveDate <= @CurrentDate
    ORDER BY EffectiveDate DESC 
UNION ALL
    SELECT TOP 1000000 *
    FROM @Dates t2
    WHERE EffectiveDate NOT IN (
                            SELECT *
                            FROM @Dates
                            WHERE EffectiveDate <= @CurrentDate
                                )
    ORDER BY EffectiveDate
) t

******* 编辑 *******

正如 HABO 所说，上述结果集不一定有保证的顺序。下面的编辑应该会解决这个问题。

SELECT *
FROM (SELECT *, ROW_NUMBER() OVER(ORDER BY EffectiveDate DESC) Sort
      FROM @Dates t1
      WHERE EffectiveDate <= @CurrentDate
    UNION ALL
      SELECT *
         ,(SELECT MAX(Sort) 
            FROM (SELECT *, ROW_NUMBER() OVER(ORDER BY EffectiveDate DESC) Sort
                    FROM @Dates t1
                    WHERE EffectiveDate <= @CurrentDate
                  ) t2
          ) 
         + ROW_NUMBER() OVER(ORDER BY EffectiveDate ASC) Sort
    FROM @Dates t3
    WHERE EffectiveDate NOT IN (SELECT *
                                FROM @Dates
                                WHERE EffectiveDate <= @CurrentDate)
) t
ORDER BY t.Sort

Answer 3

对于这种特定情况，解决方案是直截了当的；将小于当前日期和大于当前日期拆分为两个单独的列并进行相应排序：

WITH CTE AS (
    SELECT
        EffectiveDate,
        CASE WHEN EffectiveDate <= @CurrentDate THEN EffectiveDate END AS DL,
        CASE WHEN EffectiveDate >  @CurrentDate THEN EffectiveDate END AS DG
    FROM #Dates
)
SELECT * FROM CTE
ORDER BY DL DESC, DG

结果：

EffectiveDate       | DL                  | DG
====================+=====================+====================
2016-01-01 00:00:00 | 2016-01-01 00:00:00 | NULL
2015-01-01 00:00:00 | 2015-01-01 00:00:00 | NULL
2014-01-01 00:00:00 | 2014-01-01 00:00:00 | NULL
2017-01-01 00:00:00 | NULL                | 2017-01-01 00:00:00
2018-01-01 00:00:00 | NULL                | 2018-01-01 00:00:00

请注意，可以在不使用 CTE 的情况下编写查询。

Answer 4

试试这个...

IF OBJECT_ID(N'tempdb..#Dates') IS NOT NULL
    DROP TABLE #Dates
GO
CREATE TABLE #Dates
(
    EffectiveDate DATETIME2
);

DECLARE @CurrentDate DATETIME2 = '2016-06-01';
DECLARE @MinDate DATETIME2 = '0001-01-01';

INSERT INTO #Dates (EffectiveDate) VALUES ('2014-01-01');
INSERT INTO #Dates (EffectiveDate) VALUES ('2015-01-01');
INSERT INTO #Dates (EffectiveDate) VALUES ('2016-01-01');
INSERT INTO #Dates (EffectiveDate) VALUES ('2017-01-01');
INSERT INTO #Dates (EffectiveDate) VALUES ('2018-01-01');

SELECT
    EffectiveDate
FROM
(
    SELECT
        CASE
            WHEN EffectiveDate <= @CurrentDate THEN 1
            ELSE 2
        END GroupId,
        CASE
            WHEN EffectiveDate <= @CurrentDate THEN EffectiveDate
            ELSE NULL
        END Group1,
        CASE
            WHEN EffectiveDate <= @CurrentDate THEN NULL
            ELSE EffectiveDate
        END Group2,
        EffectiveDate
    FROM
        #Dates
)A
ORDER BY
    GroupId,
    Group1 DESC,
    Group2 ASC