As you likely know, Active Record supports placeholder values in queries:
User.where("email LIKE ? OR username LIKE ?", query, query)
But it is perhaps less well-known that it also supports named placeholders:
User.where("email LIKE :query OR username LIKE :query", query: query)
User.where("(fooable = :true AND foo_id = :foo_id) OR (barable = :true AND bar_id = :bar_id)", true: true, foo_id: 123, bar_id: 456)
These are great when you use the same value more than once, or to make complex queries more readable.