任何人都可以详细解释这行代码的作用吗？

Question

Idea.where("user_id = ?", id)

and also I wanted to ask, when should we pass param[:id]. I find it very confusing as to how where does rails find the parameters and how does this "params" work

Answer 1

It fetches all the records from the ideas table that have in their user_id column the value of the variable id .

For example if id is 3 this would be equivalent to:

Idea.where(user_id: 3)

The ? is a placeholder and prevents against SQL injection attacks .

Answer 2

Probably provides sql query like select * from ideas where user_id = 14 . Where 14 is the value of id variable. But first returns scope object. Query will be executed when necessary.