16.20 - Primary Index Assignment - Teradata Database - Teradata Vantage NewSQL Engine

Teradata Vantage™ SQL Fundamentals

Product
Teradata Database
Teradata Vantage NewSQL Engine
Release Number
16.20
Published
March 2019
Language
English (United States)
Last Update
2019-05-02
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In general, most Teradata Database tables require a primary index. (Some tables in the Data Dictionary do not have primary indexes and a global temporary trace table is not allowed to have a primary index.) To create a primary index, use the CREATE TABLE statement.

If you do not assign a primary index explicitly when you create a table, Teradata Database assigns a primary index, based on the following rules.

Primary Index Primary Key Unique Column Constraint Teradata Database selects the …
no YES no primary key column set to be a UPI.
no no YES first column or columns having a UNIQUE constraint to be a UPI.
no YES YES primary key column set to be a UPI.
no no no first column defined for the table to be a NUPI.

If the data type of the first column in the table is a LOB, then the CREATE TABLE operation aborts and the system returns an error message.

In general, the best practice is to specify a primary index instead of having Teradata Database select a default primary index.