Index determination and definition is an important aspect of database design.
Depending on how you choose to count them, Teradata Database supports between 11 and 21 index types.
For this and column-partitioned tables and join indexes, the absence of a primary index is counted as an index type.
The various join indexes are not necessarily mutually exclusive types. Both multitable and single-table simple join indexes can also be sparse, for example. A join index composed of virtual rows, with multiple fixed column sets appended to a single repeating column set is said to be row compressed. Whether compressed or not compressed, a join index can be any of the following types.
The twelve basic types are specified by the first level bullets in the list, while the twenty‑plus count includes the second‑level bullets included for join and non‑unique secondary indexes.
For additional information about Teradata Database indexes, see Database Design and SQL Fundamentals.