We interviewed several people previous week. Standard questions (I hope 😉 about everything. I like to ask questions about SQL and ActiveRecord
The fastest way to check database’s knowledge is asking to make query with all available statements.
I use something like select all user groups which have user with more than 100 tags on photos.
where User(name:string, group:string, id:int)
Photos and UserPhotos – simple tables.
First task is to build database. Not everyone can build that scheme.
But then I can see roots of MySQL.
Only MySQL allows grouping with fields which not in select query.
People who worked with MySQL only don’t see any problem here: “It will select data what you need”.