query.sql

WITH checkpoint_completion_counts AS (
  SELECT
    COUNT(checkpoint_completions.id) AS checkpoint_completions_count,
    checkpoints.ref AS checkpoint_ref,
    users.slug
  FROM checkpoint_completions
  INNER JOIN checkpoints ON checkpoint_completions.checkpoint_ref = checkpoints.ref
  INNER JOIN users ON users.id = checkpoint_completions.user_id
  GROUP BY 2,3
)

SELECT
  *
FROM
  checkpoint_completion_counts
WHERE checkpoint_completion_counts.slug = 'user-slug' AND checkpoint_completions_count > 1
;