Postgres window function column with Rails

问题

I'd like to use the rank() function PostgreSQL on one of my columns.

Character.select("*, rank() OVER (ORDER BY points DESC)")

But since I don't have a rank column in my table rails doesn't include it with the query. What would be the correct way to get the rank included in my ActiveRecord object?

回答1:

try this:

Character.find_by_sql("SELECT *, rank() OVER (ORDER BY points DESC) FROM characters")

it should return you Character objects with a rank attribute, as documented here. However, this may not be database-agnostic and tends to get messy if you pass around the objects.

another (expensive) solution is to add a rank column to your table, and have a callback recalculate all records' rank using .order whenever a record is saved or destroyed.

edit :

another idea suitable for single-record queries can ben seen here

来源：https://stackoverflow.com/questions/7506432/postgres-window-function-column-with-rails