Teradata allows null values for names of indexes, such as Primary Key, Unique, and Check Constraints.
Teradata identifies each index by a Unique Index Number, which is unique in the database and table on which the index is created. The Unique Index Number is equivalent to a position. Metadata Manager uses this number to generate a unique Element ID for all indexes that do not have names.
Metadata Manager also generates unique sequence numbers for constraints that do not have names to create their Element IDs.