有効期限が異なる類似のレコードをマージするにはどうすればよいですか？

Question

私が作業しているテーブルには、3つのコンポーネントがあります。

1. ID列（別のテーブルの主キー）
2. 一部のデータ列
3. 有効なfrom/to列。

値：

ID   Data From        To  
1    a    2015-01-01  2015-01-05
1    a    2015-01-06  2015-01-10
1    b    2015-01-11  2015-01-15
1    a    2015-01-16  2015-01-20
2    c    2015-01-01  2015-01-05
2    c    2015-01-06  2015-01-10

テーブルは、一定の間隔で別のデータソースの「スナップショット」を取得し、有効期限をレコードに割り当てることによって更新されます。問題は、これらのスナップショットが、その間隔中にまったく変更されなかった（異なる有効日付を持つ）レコードの重複エントリを作成することです。

連続した日付を持つ行を探し、それらをマージして単一の有効期間を割り当てることにより、テーブルのサイズを小さくしたいと考えています。例えば：

ID   Data From        To  
1    a    2015-01-01  2015-01-10
1    b    2015-01-11  2015-01-15
1    a    2015-01-16  2015-01-20
2    c    2015-01-01  2015-01-10

私が現在持っているロジックは：

1. すべての行を選択し、ID、データフィールド、および[有効開始日]フィールドで並べ替えます（連続した行のグループに含まれるため）。
2. カーソルを使用して、隣接する行の類似性を比較します。
3. それらが同じ場合は、行をマージし、有効期間を変更して両方の行を含めます。

カーソルは非常に効率が悪い（データセットが大きい）ことを理解しているので、他の方法を探しています。

Answer 1

これが連続する範囲のみの表である場合、ケースは古典的な「ギャップとアイランド」の問題として扱うことができます。この場合、連続する範囲のアイランドを分離し、最小値をとることによってそれらを「圧縮」するだけです[from]と最大値[to]島ごと。

2つのROW_NUMBER呼び出しを使用してこれを解決する確立された方法があります。

WITH islands AS
(
  SELECT
    id,
    data,
    [from],
    [to],
    island = ROW_NUMBER() OVER (PARTITION BY id       ORDER BY [from])
           - ROW_NUMBER() OVER (PARTITION BY id, data ORDER BY [from])
  FROM
    #mergeTest
)
SELECT
  id,
  data,
  [from] = MIN([from]),
  [to]   = MAX([to])
FROM
  islands
GROUP BY
  id,
  data,
  island
;

このクエリは、SQL Server 2005と同じ低バージョンで機能します。

Answer 2

この問題を解決するクエリを作成できました。複数の結合とwhileループを使用してレコードをマージします。このコードは、SQL Server 2008 R2と互換性があります。

CREATE TABLE #mergeTest
(
    [id] int NOT NULL,
    [data] date,
    [from] date NOT NULL,
    [to] date NOT NULL
);

INSERT INTO #mergeTest ([id],[data],[from],[to]) VALUES     --testing null data value handling
    (1,NULL,'2015-01-01','2015-01-05'), --1
    (1,NULL,'2015-01-05','2015-01-10'), --2
    (1,'2000-01-01','2015-01-10','2015-01-14'), --3
    (1,'2000-01-03','2015-01-14','2015-01-15'), --4
    (1,'2000-01-01','2015-01-15','2015-01-20'), --5
    (1,'2000-01-01','2015-01-20','2015-01-22'), --5
    (1,'2000-01-01','2015-01-22','2015-01-25'), --6
    (1,'2000-01-01','2015-01-25','2015-01-30'), --7
    (1,NULL,'2015-01-30','2015-02-04'), --8
    (2,'2000-01-05','2015-01-01','2015-01-05'), --9
    (2,'2000-01-05','2015-01-05','2015-01-10')  --10

SELECT * FROM #mergeTest 
GO
;

SELECT * INTO #tempSingle                               --isolate single records. Single records need no processing.
    FROM (
        SELECT  [id], [data], MIN([from]) as [from], MIN([to]) as [to],
                COUNT([id]) as [grpsz]
        FROM #mergeTest
        GROUP BY [id], [data]) AS [selection]
    WHERE [grpsz]=1;
ALTER TABLE #tempSingle
    DROP COLUMN [grpsz];
GO
;

SELECT * INTO #tempRemainingtemp                        --isolate records w/ more than 2 entries. They need to be reduced to single records
    FROM (
        SELECT  [id], [data],                           --get [id] and [data] of duplicate records
                COUNT([id]) as [grpsz]
        FROM #mergeTest
        GROUP BY [id], [data]) AS [selection]
    WHERE [grpsz]>=2;
ALTER TABLE #tempRemainingTemp
    DROP COLUMN [grpsz]
SELECT * FROM #tempRemainingtemp
SELECT * INTO #temp                                     --get all duplicate records into #temp
    FROM (
        SELECT [b].*
        FROM #tempRemainingtemp AS [a]
        JOIN #mergeTest AS [b]
        ON      [a].[id]=[b].[id]
            AND ([a].[data]=[b].[data] OR [a].[data] IS NULL AND [b].[data] IS NULL)) AS [selection];

DROP TABLE #tempRemainingtemp;
Go
SELECT * INTO #tempRemaining
    FROM #temp;
DROP TABLE #temp;
GO
;
SELECT * FROM #tempRemaining
BEGIN
SELECT t1.*, t2.[from] as [prevfrom] INTO #temp0        --filter in records where previous 'to' date matched current 'from' date when grouped by id and data
    FROM #tempRemaining AS t1
    JOIN #tempRemaining AS t2
    ON      t2.[to] = t1.[from]
        AND t1.[id] = t2.[id]
        AND ([t1].[data]=[t2].[data] OR [t1].[data] IS NULL AND [t2].[data] IS NULL)

SELECT t1.*, t2.[prevfrom] INTO #temp1                  --add records that did not have a previous 'to' date b/c they were the extreme records in their group
    FROM #tempRemaining AS t1
    LEFT JOIN #temp0 AS t2
    ON      t1.[id]=t2.[id]
        AND ([t1].[data]=[t2].[data] OR [t1].[data] IS NULL AND [t2].[data] IS NULL)
        AND t1.[from] = t2.[from];

DROP TABLE #temp0;

SELECT t1.*, t2.[to] as [nextto] INTO #temp2            --filter in records where current 'to' date matched next 'from' date when grouped by id and data
    FROM #temp1 AS t1
    JOIN #temp1 AS t2
    ON      t2.[from] = t1.[to]
        AND t1.[id] = t2.[id]
        AND ([t1].[data]=[t2].[data] OR [t1].[data] IS NULL AND [t2].[data] IS NULL);

SELECT t1.*, t2.[nextto] INTO #temp                     --add records that did not have a next 'from' date b/c they were the extreme records in their group
    FROM #temp1 AS t1
    LEFT JOIN #temp2 AS t2
    ON      t1.[id]=t2.[id]
        AND ([t1].[data]=[t2].[data] OR [t1].[data] IS NULL AND [t2].[data] IS NULL)
        AND t1.[from] = t2.[from];

DROP TABLE #temp2;
DROP TABLE #temp1;

DELETE FROM #temp                                       --delete redundant records
    WHERE   [prevfrom] IS NOT NULL
        AND [nextto] IS NOT NULL;

WITH cte AS (                                           --select records that got reduced to singles and insert them into singles account
    SELECT [id], [data], [from], [to]
        FROM [#temp]
        WHERE   [prevfrom] IS NULL
            AND [nextto] IS NULL)
DELETE FROM cte
OUTPUT deleted.* INTO #tempSingle

/* ALL DUPLICATE RECORDS ARE NOW REDUCED TO PAIRS*/

SELECT * FROM #temp;
ALTER TABLE #temp
    DROP COLUMN [nextto],[prevfrom]                     --remove helper columns
END

SELECT TOP 1 * INTO #temptemp                           --create temporary tables for storage
    FROM #temp
SELECT TOP 1 * INTO #tempResult
    FROM #temp
TRUNCATE TABLE #temptemp
TRUNCATE TABLE #tempResult

WHILE EXISTS(SELECT [id] from #temp)
BEGIN
    WITH cte AS (
            SELECT TOP 2 *                              --select pair
                FROM #temp
                ORDER BY [id],[data],[from])
        DELETE FROM cte                                 --delete from original table
        OUTPUT deleted.* INTO #temptemp;
    INSERT INTO #tempResult                             --insert merged record into result table
        SELECT t1.[id], t1.[data], t1.[from], t2.[to]
        FROM #temptemp AS t1
        JOIN #temptemp AS t2
        ON t1.[from]<t2.[from];
    TRUNCATE TABLE #temptemp;                           --empty temporary storage table
END;

TRUNCATE TABLE #mergeTest;                              --insert single records and merged records into original table
INSERT INTO #mergeTest
    SELECT * FROM #tempResult;
INSERT INTO #mergeTest
    SELECT * FROM #tempSingle;

SELECT * FROM #mergeTest
    ORDER BY [id],[from];

Answer 3

連続していても別々にしておく必要がある、連続していない日付範囲がある場合のために、私はこの解決策を思いつきました：

SQL Fiddleを参照

WITH lag_info AS (
  SELECT
    ID,
    Data,
    [From],
    [To],
    lag([To], 1, NULL) OVER (PARTITION BY ID ORDER BY [From]) AS PrevTo,
    lag(Data, 1, NULL) OVER (PARTITION BY ID ORDER BY [From]) AS PrevData
  FROM dat
),
segmented AS (
  SELECT
    ID,
    Data,
    [From],
    [To],
    -- new interval if non-contigous or data changed
    -- if it's null, it means that it's the first entry for the ID, which means it's a new interval
    CASE
      WHEN [PrevTo] IS NULL
        OR PrevData IS NULL
        OR DATEDIFF(DAY, [PrevTo], [From]) > 1
        OR Data <> PrevData
      THEN 1
      ELSE 0
    END AS is_new_interval
  FROM lag_info
),
segmented_marked AS (
  SELECT
    ID,
    [From],
    [To],
    Data,
    -- increment only when new data is detected, using a running sum
    sum(s.is_new_interval)
      OVER (PARTITION BY ID ORDER BY [From] ROWS BETWEEN UNBOUNDED PRECEDING AND 0 FOLLOWING)
                                AS interval_id
  FROM segmented s
)
SELECT
  ID,
  min([From]) AS [From],
  max([To]) AS [To],
  Data
FROM segmented_marked
GROUP BY ID, Data, interval_id