16.20 - PRIMARY KEY Constraints - Teradata Database - Teradata Vantage NewSQL Engine

Teradata Vantage™ SQL Data Definition Language Detailed Topics

Teradata Database
Teradata Vantage NewSQL Engine
Release Number
March 2019
Content Type
Programming Reference
Publication ID
English (United States)

The primary key of a table is a column set that uniquely identifies each row of that table. See Teradata Vantage™ - Database Design, B035-1094. You cannot define more than 1 primary key for a table. Primary keys, which are a logical construct in the relational model, are usually implemented physically as the unique primary index.

To create a composite, or multicolumn, primary key for a table, you must specify the PRIMARY KEY constraint at the table level, not the column level.

Columns defined with a data type from the following list cannot be a component of a PRIMARY KEY constraint.
  • BLOB
  • CLOB
  • BLOB-based UDT
  • CLOB-based UDT
  • Period
  • Geospatial

When a table has a nonunique primary index, you should consider defining its primary key explicitly using the PRIMARY KEY clause. Primary and other alternate keys are also used with foreign keys to enforce referential integrity relationships between tables (see Standard Referential Integrity Constraints, Batch Referential Integrity Constraints, and Referential Constraints).