Counts the number of (contributor) reviews per committer for a specific quarter

reviews_per_quarter.sql

-- The SQL below counts exclusively reviews of non-committers.
SELECT count(*) reviews, committer
FROM
  (SELECT c.author author,
          c.committer committer,
          CASE
              WHEN c.author_timestamp > phonebook.first_commit THEN 1
              ELSE 0
          END is_committer
   FROM git_commits c
   LEFT JOIN
     (SELECT committer,
             min(commit_timestamp) first_commit
      FROM git_commits
      GROUP BY committer) phonebook ON c.author = phonebook.committer
   WHERE commit_timestamp >= cast('2020-07-01' AS date)
     AND commit_timestamp < cast('2020-10-01' AS date))
WHERE is_committer = 0
GROUP BY committer
ORDER BY reviews DESC