SQL Join Operator Functions

These are functions that can be used in the join argument in a select option hash:

- join_inner(): specifies an inner join
- join_left(): specifies a left outer join
- join_right(): specifies a right outer join

Note
  for join functions, explicit join columns do not need to be specified in the case that a foreign key in one table exists to the primary key of the other table; in this case this information is assumed for the join automatically