特定列的行數和最後一行的顯示數

Question

我必須計算列中相同值的行數，並顯示最後一列的計數值。下面是我的方案

表1

Col_A Col_B Col_C 
a  1  a1 
a  2  a2 
a  3  a3 
a  4  a4 
a  5  a5 
a  6  a6 
b  7  a7 
b  8  a8 
b  9  a9 
b  10  a10 
e  7  a11 
e  1  a12 
e  4  a13

而顯示數據，我應該算在爲col_a相同的值，並顯示如下圖所示

Col_A Col_B Col_C Col_D 
a  1  a1 
a  2  a2 
a  3  a3 
a  4  a4 
a  5  a5 
a  6  a6  6 
b  7  a7 
b  8  a8 
b  9  a9 
b  10  a10  4 
e  7  a11 
e  1  a12 
e  4  a13  3

感謝，

Answer 1

你可以檢查，看看是否ROW_NUMBER等於在（計數（）），如果是顯示計數

SELECT [Col_A], 
     [Col_B], 
     [Col_C], 
     (CASE WHEN ROW_NUMBER() OVER (PARTITION BY [Col_A] ORDER BY [Col_B]) = COUNT(*) OVER (PARTITION BY COL_A) 
      THEN COUNT(*) OVER (PARTITION BY COL_A) END) AS Col_D 
FROM Table1 

Answer 2

這是一種方式去做吧。鉛（）來檢查，如果這是一組的最後一行，並ROW_NUMBER用來計算行量：使用反向行號應太

select Col_A, Col_B, Col_C, case when isnull(NextA,'') != Col_A then RN end 
from (
    select 
    *, 
    row_number() over (partition by Col_A order by Col_C) as RN, 
    lead(Col_A) over (order by Col_A, Col_C) as NextA 
    from Table1 
) X 

爲2008：

select Col_A, Col_B, Col_C, case when RN2 = 1 then RN end 
from (
    select 
    *, 
    row_number() over (partition by Col_A order by Col_C asc) as RN, 
    row_number() over (partition by Col_A order by Col_C desc) as RN2 
    from Table1 
) X 

Answer 3

SQL 2008有ROW_NUMBER()

DEMO

SELECT X.*, (CASE WHEN rn=1 THEN total END) as count_A 
FROM (SELECT Col_A, 
       Col_B, 
       Col_C, 
       row_number() over 
       (partition by Col_A order by Col_C DESC) as rn 
     from test 
    ) X 
join (
     SELECT [Col_A] , 
       count([Col_A]) as total 
     FROM test GROUP BY [Col_A] 
    ) Y 
    ON X.[Col_A] = Y.[Col_A] 
ORDER BY X.Col_A,   
     X.Col_C 

輸出

編輯V2.0：這大概應太和犯規需要JOIN

SELECT X.*, 
     (CASE WHEN rn=1 
      THEN MAX(rn) OVER (partition BY X.col_a) 
     END) as count_A 
FROM (SELECT Col_A, 
       Col_B, 
       Col_C, 
       row_number() over (partition by Col_A order by Col_C DESC) as rn 
     from test 
    ) X 
ORDER BY X.Col_A,   
     X.Col_C