Techniques for optimizing outer joins in database operations are provided. In an embodiment, a query having an outer join with a GROUP BY clause is rewritten and expanded to expand a first level partition of that GROUP BY clause to produce a modified query. In another situation, rows associated with processing a query are each row split and then hashed based at least in part on attributes of the outer join predicate. A left outer join is performed and a global aggregation processed to produce a spooled table to process the query.