Using arel to query SQL functions

arel_based.rb

dc = Arel::Nodes::NamedFunction.new "DATE", [ p[:created_at] ] ## second argument must be an array

## Sub this...
arel.project("DATE(`photos`.`created_at`)")

## For this...
arel.project(dc.to_sql)

arel.to_sql >> "SELECT DATE(`photos`.`created_at`) FROM `photos` INNER JOIN `votes` ON `photos`.`id` = `votes`.`photo_id`"

cast.rb

time = Arel::Nodes::NamedFunction.new "CAST", [ p[:created_at].as("TIME") ]

time.to_sql >> "CAST(`photos`.`created_at` AS TIME)"

sql_based.rb

p = Arel::Table.new("photos")
v = Arel::Table.new("votes")

## We aren't using SQL here
arel = p.join(v).on(p[:id].eq(v[:photo_id]))

## So why should we here
arel.project("DATE(`photos`.`created_at`)")

arel.to_sql >> "SELECT DATE(`photos`.`created_at`) FROM `photos` INNER JOIN `votes` ON `photos`.`id` = `votes`.`photo_id`"