Aggregation is performed on rows satisfying criteria that are represented by predicates in an SQL statement.
If an aggregate function executes, one of the following statements appears in db2expln output:
Aggregation Predicate Aggregation Partial Aggregation Partial Predicate Aggregation Hashed Partial Aggregation Hashed Partial Predicate Aggregation Intermediate Aggregation Intermediate Predicate Aggregation Final Aggregation Final Predicate Aggregation
Predicate aggregation means that the aggregation operation was processed as a predicate when the data was accessed.
The aggregation statement is followed by another statement that identifies the type of aggregate function that was performed:
The specific aggregate function can be derived from the original SQL statement. A single record is fetched from an index to satisfy a MIN or MAX operation.
Group By Column Function(s) Single Record
If predicate aggregation has been performed, there is an aggregation completion operation and corresponding output:
Aggregation Completion Partial Aggregation Completion Hashed Partial Aggregation Completion Intermediate Aggregation Completion Final Aggregation Completion