- An alias is required for a subselect or view.
- An alias is optional for a base table. The default alias is the table name.
- If the SQL-MapReduce function uses a table or view as input more than once, each input must have a different alias.For example:
SELECT * FROM union_inputs ( ON t AS t1 PARTITION BY ANY ON t AS t2 DIMENSION mode ('roundrobin') );
Omitting the aliases causes an error:SELECT * FROM union_inputs ( ON t PARTITION BY ANY ON t DIMENSION mode ('roundrobin') ); ERROR: input alias T in SQL-MR function UNION_INPUTS appears more than once