通过在rails3中使用IN运算符来查找位置。

select name from appointments where location_id in (2,3,4)

PostgreSQL

a = [2,3,4]
Appointment.select(:name).where(\"location_id IN ?\", a)

ActiveRecord::StatementInvalid: PGError: ERROR:  syntax error at or near \"2\"
LINE 1: ... FROM       \"appointments\"  WHERE     (location_id IN 2,3,4)
                                                                 ^
: SELECT     name FROM       \"appointments\"  WHERE     (location_id IN 2,3,4)

Appointment.select(:name).where(:location_id => [2,3,4])

Appointment.select(:name).where(\"location_id IN (?)\", a)

?