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Collections are a way for you to organize kata so that you can create your own training routines. Every collection you create is public and automatically sharable with other warriors. After you have added a few kata to a collection you and others can train on the kata contained within the collection.
Get started now by creating a new collection.
I agree with the comments. Please change the statement of the exercise to highlight that the columns selected HAVE TO BE aliased to age_min and age_max. Otherwise it can be a bit disheartening for beginners.