SQL Challenges · THE GREAT DUCK MIGRATION!
The Incomplete Roster
Difficulty: hard
Coach Waddles flips through training rosters with growing concern. We have four core disciplines - swimming, flying_speed, running, and diving. Most of our athletes have trained in all four, but some have gaps in their experience! I need to identify ducks who competed in exactly three sports. These athletes require targeted training in their missing discipline before we depart. Their near-complete skill sets make them valuable, but that one gap could be dangerous!
Your task
Return the sum of SSNs for all ducks who have competed in exactly 3 different sports throughout their career. You will be working with `duck_athletes` and `performance_records` tables.