Aggregate Join Indexes
An aggregate join index is a database object created using the CREATE JOIN INDEX statement, but specifying one or more columns that are derived from an aggregate expression. An aggregate join index is a join index that specifies MIN, MAX, SUM, COUNT, or that extracts a DATE value aggregate operations. No other aggregate functions are permitted in the definition of a join index; however, most of the other simple aggregate functions can be derived from these using column expressions. You can create aggregate join indexes as either single‑table or as multitable join indexes. Aggregate join indexes can also be sparse (see “Sparse Join Indexes” on page 556).