The ANSI SQL:2011 standard supports 3 comparison options for ordering definitions:
- MAP
- RELATIVE
- STATE
Teradata Database does not support the STATE and RELATIVE comparisons because they do not mesh well with the Teradata parallel architecture. The issue that makes these options problematic is that there is a strong relationship between the concepts of equality and the hash values that Teradata Database generates for many of its join strategies. Two values that are equal in the relational use of the concept must generate hash values that are also equal.
The MAP ordering approach enables Teradata Database to generate internally an appropriate hash value for the UDT, enabling all Optimizer join strategies to function properly.