This advanced SQL exercise is part of the book: Advanced SQL – Practical Techniques and Use-Cases, which includes 100 day-to-day SQL challenges (and solutions), need-to-know advanced features, and key concepts.
 

An interesting SQL exercise. Given the following table of dates:


CREATE TABLE dates
(date_id date,
period int)
GO

This table represents all days in the year 2016; each day is assigned to a specific period. These periods were defined arbitrarily, based on the following rules:

  • A period whose number is 1 was defined for the months: 1, 3, 5, 7, 9
  • A period whose number is 2 was defined for the months: 2, 4, 6, 8
  • A period whose number is 3 was defined for the months: 10, 11, 12

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