Primary Indexes and Primary AMP Indexes
Teradata Database tables can have 0 or 1 primary index or primary AMP index. If you do not define either PRIMARY INDEX, PRIMARY AMP INDEX, or NO PRIMARY INDEX explicitly when you create a table, then a default primary index for a table may be defined or the table may default to have no primary index (see “Primary Index Defaults” on page 211 for details).
Use the CREATE TABLE statement to create primary indexes (see “CREATE TABLE” in SQL Data Definition Language).
Note that Teradata does not use the term primary index in the same way it is commonly used to describe a clustered index in an indexing system based on B+ trees.
Data accessed using a primary index or primary AMP index is always a one-AMP operation. This is true whether a primary index is unique or nonunique, and whether it is partitioned or nonpartitioned. This is true whether a primary AMP index is row partitioned or not.