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  3. Exploratory Data Analysis in SQL

Exercise

Date truncation

Unlike date_part() or EXTRACT(), date_trunc() keeps date/time units larger than the field you specify as part of the date. So instead of just extracting one component of a timestamp, date_trunc() returns the specified unit and all larger ones as well.

Recall the syntax:

date_trunc('field', timestamp)

Using date_trunc(), find the average number of Evanston 311 requests created per day for each month of the data. Ignore days with no requests when taking the average.

Instructions

100 XP
  • Write a subquery to count the number of requests created per day.
  • Select the month and average count per month from the daily_count subquery.