T-SQL How to select count of one column's values where another column's values are the same

Question

How to select count of Label where Part is the same?

Part  |  Label
------+-------
  a   |    L1
  a   |    L2
  a   |    L3
  b   |    L1
  b   |    L2  

Expected results:

Part  |  LabelCount
------+------------
  a   |    3
  b   |    2

Notes: All data types are strings. I've tried partitioning to get the max row number, but the MAX function on ROW_NUMBER() is unresponsive the way I've been doing it, and it's just been returning all rows whether I use MAX or not.

;WITH RowNumCTE AS 
(
    SELECT
        [PartName],
        ROW_NUMBER() OVER (PARTITION BY [Part] ORDER BY [Label] ASC) AS rn
    FROM 
        [PartTable]
)
SELECT DISTINCT   
    [Part],
    MAX([rn]) AS [LabelCount]
FROM
    RowNumCTE
GROUP BY
    [Part], [rn]

Actual results:

Part  |  LabelCount
------+------------
  a   |    1
  a   |    2
  a   |    3
  b   |    1
  b   |    2

I've run down the list of similar questions in StackOverflow, like this one , but don't see how to apply the answers to this situation.

Answer 1

You seem to just want group by :

select part, count(*) as labelcount
from t
group by part;

If you have duplicate labels on a part, then:

select part, count(distinct label)
. . .

Answer 2

simple group by

select part,count(*) from t 
group by part

Answer 3

Your approach to the expected o/p is wrong and very complex.

Your desired o/p is no where related to sub partitioning of groups as you have done via partition by etc but was rather a simple group by as already by the above answers.

      select part,count(*) from t 
       group by part -- as only partwise 
       count is required