17.10 - PRIMARY KEY Constraints - Advanced SQL Engine - Teradata Database

Teradata Vantage™ - SQL Data Definition Language Detailed Topics

Product
Advanced SQL Engine
Teradata Database
Release Number
17.10
Release Date
July 2021
Content Type
Programming Reference
Publication ID
B035-1184-171K
Language
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
  • ARRAY
  • VARRAY
  • 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).