How to group by week in postgresql

Question

I\'ve a database table commits with the following columns:

id | author_name | author_email | author_date (timestamp) | total_lines

Answer 1

If you have multiple years, you should take the year into account as well. One way is:

SELECT date_part('year', author_date::date) as year,
       date_part('week', author_date::date) AS weekly,
       COUNT(author_email)           
FROM commits
GROUP BY year, weekly
ORDER BY year, weekly;

A more natural way to write this uses date_trunc():

SELECT date_trunc('week', author_date::date) AS weekly,
       COUNT(author_email)           
FROM commits
GROUP BY weekly
ORDER BY weekly;