Whenever I wanted to use placeholders in raw SQL query fragments in Rails, I would use and end up writing — ? Post.where('published_at > ?', some_time) What if I wanted to add another condition that checks against the same value in ? some_time Post.where('published_at > ? OR saved_at > ?', some_time, some_time) To be perfectly honest, writing such code never bothered me and I did not put in the little effort that was needed to see if there was a better way to do this. One day I was pairing with one of my colleagues, , and she had something that looked like in her query fragments, like this — . Preethi Kumar symbols published_at > :date I had seen nothing like that before and I was wondering if that was some esoteric feature or something :D database That’s when I got to know that you can use named placeholders in query fragments and pass in a hash for to resolve those values. ActiveRecord And now, I can happily re-write my statement as — Post.where('published_at > :time OR saved_at > :time', selected_time: some_time) Easily one can see many small wins with this like — Longer queries become more readable, provided the placeholder names are well thought out. Reduces cognitive overhead. You’re not repeatedly writing out variables that are used multiple times. Positional coupling is broken.
