Se você usa PostgreSQL, pode usar
row_number()
:SELECT t.*
FROM (
SELECT *, row_number() OVER(ORDER BY id ASC) AS row
FROM yourtable
) t
WHERE t.row % 5 = 0
row_number()
:SELECT t.*
FROM (
SELECT *, row_number() OVER(ORDER BY id ASC) AS row
FROM yourtable
) t
WHERE t.row % 5 = 0