问题
My goal is to query Items by their user_id, year created, and month created. I am using sqlite3 in development and postresql in production on Heroku.
I want to do something like this:
items.where("user_id = '?' AND strftime('%Y', created_at) = '?' AND strftime('%-m', created_at) = '?' ", 6, 2015, 3)
But it returns no records.
This works:
items.where("user_id = '?' AND strftime('%Y', created_at) = '?' ", 6, 2015)
But this returns no records:
items.where("user_id = '?' AND strftime('%-m', created_at) = '?' ", 6, 3)
Am I using the '%-m' format incorrectly?
回答1:
I would not use different databases in development and production, use the same one. Just configure postgresql on your localhost and change your query to something like:
user.items.where("date_part('year', created_at) = :year AND date_part('month', created_at) = :month", year: 2015, month: 6)
That's assuming that you have the associations setup between items and users, then you don't need to query on user_id as well.
来源：https://stackoverflow.com/questions/29739281/ruby-strftime-m-not-working-in-query