Question

I have three models

• Tag => :id, :name
• Tagging => :id, :tag_id, :post_id
• Post => :id, :summary

I know the id of the tag. I would like to query for all of the posts that have a specific tag_id, through the Taggings model.

Something like

@post = Post.joins(:taggings).where(:tag_id => 17)

but this doesn’t work because it is looking for the tag_id in the Post model and not the Tagging model.

I’m not sure how to do this.

Answer 1

Using the .where format you can pass a string like .where(“taggings.tag_id = ?”, 17) to qualify the joined taggings table.