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.
- BLOB-based UDT
- CLOB-based UDT
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).