Instruction
Wow, you're making great progress! Here's another one.
Exercise
Group all flights by year. Show the year, and calculate the average delay time for each of those years. Name the columns Year and AvgDelay.

Wow, you're making great progress! Here's another one.
Group all flights by year. Show the year, and calculate the average delay time for each of those years. Name the columns Year and AvgDelay.
