Attributes and semantics of duplicate insignificance that are inherent or inferred in a database language statement are detected. Also, a join operation that is inherent or inferred in the database language statement is detected and examined for join semantics. The join semantics specifies or refers to a driving table to be subjected to a hash join operation that may populate one or more hash buckets. The optimizer and the execution layers may use cost estimation or heuristics to assign the left and right table roles to the tables involved in the join. The hash join operation removes left table duplicates during population of the hash buckets, resulting in full or partial duplicate elimination that occurs during the hash join operation.