How to properly group rows?

Question

SQL

for example there is a table
in the column [Column2] there are repeating rows and I need to output without repeating.
How can I do that ? so that the result is

Answer 1

If without `id`, then SELECT DISTINCT, otherwise GROUP BY

Answer 2

You can use window functions to solve:

-- вариант 1
SELECT s.id, s.Column1, s.Column2 
FROM (
    SELECT t.id, t.Column1, t.Column2, RN = ROW_NUMBER() OVER (PARTITION BY t.Column2 ORDER BY id ASC)
    FROM test1 AS t
) S
WHERE S.RN = 1

-- вариант 2 с CTE
;WITH S AS (
    SELECT t.id, t.Column1, t.Column2, RN = ROW_NUMBER() OVER (PARTITION BY t.Column2 ORDER BY id ASC)
    FROM test1 AS t 
)
SELECT s.id, s.Column1, s.Column2
FROM s
WHERE S.RN = 1

Answer 3

Without window functions:

select 
id,
Column1,
Column2
from your_table
where id in (
  select min(id) from your_table 
  group by Column2
  )
order by id;