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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.
Maybe it is because of this kata supports only PostgreSQL?
Have not you tried to add types ???
Like here
weekdays(date1 DATE, date2 DATE)