How to use created_at field in Ruby on Rails in mysql query?

Question

MySQL

Usually this thing works STR_TO_DATE(string, '%d.%m.%Y'), example:

Post.where("STR_TO_DATE('02.11.2016', '%d.%m.%Y') < STR_TO_DATE('01.01.2017', '%d.%m.%Y')")

But if you use the created_at field, it doesn't work, for example:

Post.where("STR_TO_DATE(created_at, '%d.%m.%Y') < STR_TO_DATE('01.01.2017', '%d.%m.%Y')")

How to solve the problem?

Answer 1

From the comments, created_at is a normal timestamp or datetime field. Therefore, not only does it not need to be cast to a string and parsed again into a date (with the wrong format, moreover), but it is also very harmful to do so, because precludes the use of an index.
The date can be formatted in Ymd format on the application, this is already more convenient.