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Customer Behavior Analysis in SQL

Introduction
Customer cohorts
Summary

Instruction

Very well done! Let's do one more exercise.

Exercise

Find the registration count for each week in each year. Show the following columns: registration_year, registration_week, and registration_count. Order the results by the year and week.

Note: When a week overlaps two years, different databases will behave differently. You need to check your database's documentation to see how your database will classify days in this week. For example: let's consider two days: December 30th, 2019 and January 5th, 2020 (Monday and Sunday of the same week).

  • In PostgreSQL (which we use in this course): the database treats that week as one week: every day will be classified as week 1 of 2020.
  • In SQL Server: the database splits that week's days into two different weeks. December 30th and 31st will be classified as week 53 of 2019, while January 1st—5th will be classified as week 1 of 2020.

Stuck? Here's a hint!

To get the week number from a date, use:

DATE_PART('week', registration_date)