When a GROUP BY clause is used in a query that also includes an aggregate function, the aggregate function produces a value for each group. These values are called vector aggregates. The Vector Aggregate statement from SHOWPLAN indicates that the query includes a vector aggregate.
The following example includes a vector aggregate:
SELECT title_id, AVG(qty) FROM sales GROUP BY title_id
STEP 1 The type of query is SELECT (into a worktable) GROUP BY Vector Aggregate FROM TABLE sales Nested iteration Table Scan TO TABLE Worktable 1 STEP 2 The type of query is SELECT FROM TABLE Worktable 1 Nested iteration Table Scan