Question

How could I call the custom sql function on arel?
What I mean: we can do so:
arel_table[:c].sum.as(‘summarizing’)

How could I do so:
arel_table[:created_at].date_format(‘%Y-%m-%d’).as(‘something’)?

Answer 1

there are only few functions that are predefined like sum, count, average, minimum etc.
If you want to use something custom I believe you should use Arel::Nodes::NamedFunction and database specific functions. For example for PostgreSQL it could be sth like this:

t = Country.arel_table
func = Arel::Nodes::NamedFunction.new("to_char", [ t[:created_at], "YYYY-MM-DD"]).as("pretty_date")
query = t.project(func)

query.to_sql # => SELECT to_char("countries"."created_at", 'YYYY-MM-DD') AS pretty_date FROM "countries" 

I hope this will help you somehow, cheers