为相同的序列元素分配多次连续的重复

问题描述

我正在使用如下所示的 sql Server 表：

差异	nom	rec_num
-7	abc	9
-6	abc	9
-5	abc	7
-4	abc	6
-3	abc	6
-2	abc	6
-1	abc	13
-7	fav	7
-6	fav	9
-5	fav	9
-4	fav	13
-3	fav	7
-2	fav	7
-1	fav	7

真正的桌子要大得多，这是样本。

我需要为表格的每个 rec_num 分配它们连续重复的次数。比如有一个序列5 5 4 4 4 3 5 5 5 5 1，那么工作的结果应该是2 2 3 3 3 1 4 4 4 4 1。我需要的是连续的重复次数，而不是重复的总数。

使用 ROW_NUMBER 的组合：

with cte as (
  select diff,nom,rec_num,row_number() over (partition by nom order by nom,diff desc) rn1,row_number() over (partition by nom,rec_num order by nom,diff desc) rn2
  from t)
  
 select diff,rn1 - rn2 order by nom,diff desc) as con_repeats
from cte

我得到了下表

差异	nom	rec_num	con_repeas
-1	abc	13	1
-2	abc	6	1
-3	abc	6	2
-4	abc	6	3
-5	abc	7	1
-6	abc	9	1
-7	abc	9	2
-1	fav	7	1
-2	fav	7	2
-3	fav	7	3
-4	fav	13	1
-5	fav	9	1
-6	fav	9	2
-7	fav	7	1

但我需要这样的表格：

差异	nom	rec_num	con_repeas
-1	abc	13	1
-2	abc	6	3
-3	abc	6	3
-4	abc	6	3
-5	abc	7	1
-6	abc	9	2
-7	abc	9	2
-1	fav	7	3
-2	fav	7	3
-3	fav	7	3
-4	fav	13	1
-5	fav	9	2
-6	fav	9	2
-7	fav	7	1

我该怎么做？

解决方法

您只需使用 group by

即可完成此操作

with x as (
    select nom,rec_num,Count(*) n
    from t
    group by nom,rec_num
)
update t set t.con_repeats=x.n
from x
join t on t.nom=x.nom and t.rec_num=x.rec_num

见Fiddle

编辑

澄清问题后，需要不同的解决方案，这使用window functions来识别重复值的岛和updatable CTE将每个岛组的max count应用到源表：

with groups as (
    select t.*,Dense_Rank() over (partition by nom order by (rn - rn2),rec_num) as grp,Row_Number() over (partition by nom,(rn - rn2),rec_num order by diff) as c
    from(
        select t.*,row_number() over (partition by nom order by diff) as rn,rec_num order by diff) as rn2
        from t
    )t
),cnt as (
    select *,Max(c) over (partition by nom,grp) maxc
    from groups
)
update cnt set con_repeats=maxc;

select * from t;

看到这个New fiddle

,

-- Please see if this helps.

SELECT t1.*,repeats FROM tbl t1
INNER JOIN 
    (SELECT repeats,nom,rec_num FROM (
        (SELECT COUNT(*) repeats,rec_num FROM tbl GROUP BY nom,rec_num))t
     ) t2
ON t2.nom = t1.nom and t2.rec_num = t1.rec_num
ORDER BY nom,diff DESC