left join in hive

would anyone kindly answer the question below?

Is left join outer join or inner join in hive?

(Do we need to type left “outer” join in order to do the outer join? or simply left join works as outer?)

Answer

Just like in most, if not all, databases, the outer word is optional in left [outer] join, while both syntaxs have the exact same meaning.

A quick glance at the hive documentation:

Hive supports the following syntax for joining tables:

join_table:
    table_reference [INNER] JOIN table_factor [join_condition]   
  | table_reference {LEFT|RIGHT|FULL} [OUTER] JOIN table_reference join_condition   
  | table_reference LEFT SEMI JOIN table_reference join_condition   
  | table_reference CROSS JOIN table_reference [join_condition] (as of Hive 0.10)