The DATE, TIME, and DTTM indexes have performance consistent with the HNG index. Compared to HNG, DATE, TIME, and DTTM indexes are generally faster (up to twice as fast) than HNG in the supported cases. In the special cases discussed in the “Recommended use” section, the performance of the DATE, TIME, and DTTM indexes is even better. Therefore, an HNG index is not necessary in addition to a DATE, TIME, or DTTM index on a column of DATE, TIME, DATETIME, or TIMESTAMP data type.
