获取所有连续行的不同值？

Question

我正在努力解决这个问题，因为它涉及到连续行的比较。我正在尝试对相差某个数字的值进行分组。例如，假设我有这张表：

CREATE TABLE #TEMP (A int, B int)

-- Sample table
INSERT INTO #TEMP VALUES 
(3,1), 
(3,2), 
(3,3),
(3,4),
(5,1),
(6,1),
(7,2),
(8,3),
(8,4),
(8,5),
(8,6)

SELECT * FROM #TEMP

DROP TABLE #TEMP

假设我必须将所有相差 1 的值分组为具有相同 A 的值。然后我试图获得这样的输出：

A B GroupNo
3 1 1
3 2 1
3 3 1
3 4 1
5 1 2
6 1 3
7 2 4
8 3 5
8 4 5
8 5 5
8 6 5

(3,1) (3,2) (3,3) (3,4) 和 (8,3) (8,4) (8,5) (8,6) 已被放入同一组，因为它们的值相差 1。我将首先展示我的尝试：

CREATE TABLE #TEMP (A int, B int)

-- Sample table
INSERT INTO #TEMP VALUES 
(3,1), (3,2), (3,3), (3,4), (5,1), (6,1), (7,2),
(8,3), (8,4), (8,5), (8,6)

-- Assign row numbers and perform a left join
-- so that we can compare consecutive rows
SELECT ROW_NUMBER() OVER (ORDER BY A ASC) ID, * 
INTO #TEMP2
FROM #TEMP

;WITH CTE AS
(
    SELECT X.A XA, X.B XB, Y.A YA, Y.B YB
    FROM #TEMP2 X
    LEFT JOIN #TEMP2 Y
    ON X.ID = Y.ID - 1
    WHERE X.A = Y.A AND
    X.B = Y.B - 1
)
SELECT XA, XB
INTO #GROUPS
FROM CTE
UNION 
SELECT YA, YB
FROM CTE
ORDER BY XA ASC 

-- Finally assign group numbers
SELECT X.XA, X.XB, Y.GID
FROM #GROUPS X
INNER JOIN
(SELECT XA, ROW_NUMBER() OVER (ORDER BY XA ASC) GID
    FROM #GROUPS Y
    GROUP BY XA
) Y
ON X.XA = Y.XA

DROP TABLE #TEMP
DROP TABLE #TEMP2
DROP TABLE #GROUPS

我将在一个大表（大约 3000 万行）上执行此操作，因此我希望有更好的方法来处理任意值（例如，不仅相差 1，还可以是 2 或 3我将在稍后将其合并到一个程序中）。关于我的方法是否没有错误以及是否可以改进的任何建议？

Answer 1

对于它们相差一个的情况，您可以使用

;WITH T AS
(
SELECT *,
       B - DENSE_RANK() OVER (PARTITION BY A ORDER BY B) AS Grp
FROM #TEMP
)
SELECT A,
       B,
       DENSE_RANK() OVER (ORDER BY A,Grp) AS GroupNo
FROM T
ORDER BY A, Grp

更一般的

DECLARE @Interval INT = 2

;WITH T AS
(
SELECT *,
       B/@Interval - DENSE_RANK() OVER (PARTITION BY A, B%@Interval ORDER BY B) AS Grp
FROM #TEMP
)
SELECT A,
       B,
       DENSE_RANK() OVER (ORDER BY A, B%@Interval,Grp) AS GroupNo
FROM T
ORDER BY A, GroupNo

Answer 2

declare @Diff int = 1

;with C as
(
  select A, 
         B,
         row_number() over(partition by A order by B) as rn
  from #TEMP
),
R as
(
  select C.A,
         C.B,
         1 as G,
         C.rn
  from C
  where C.rn = 1
  union all
  select C.A,
         C.B,
         G + case when C.B-R.B <= @Diff 
               then 0
               else 1
             end,
         C.rn
  from C
    inner join R
       on R.rn + 1 = C.rn and
          R.A = C.A       
)
select A,
       B,
       dense_rank() over(order by A, G) as G
from R
order by A, G