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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.
In general, it's presumed to be good practice to always alias your tables - according to one of my more experienced developer friends. I imagine it becomes "best practice" when you have multiple tables in a query.
The error message clearly says what's wrong. You should read the documentation about how to use
GROUP BYand aggregate functions correctly.Read the error message:
It's
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