How to select most frequent value in a column per each id group?

Question

I have a table in SQL that looks like this:

user_id | data1
0       | 6
0       | 6
0       | 6
0       | 1
0       | 1
0       | 2
1       | 5
1       | 5
1         


        

Answer 1

You can use a window function to rank the userids based on their count of data1.

WITH cte AS (
SELECT 
    user_id 
  , data1
  , ROW_NUMBER() OVER (PARTITION BY user_id ORDER BY COUNT(data1) DESC) rn
FROM dbo.YourTable
GROUP BY
  user_id,
  data1)

SELECT
    user_id,
    data1
FROM cte WHERE rn = 1