15.00 - Why Teradata Database Does Not Support The ANSI SQL STATE and RELATIVE Comparison Options - Teradata Database

Teradata Database SQL Data Definition Language Detailed Topics

prodname
Teradata Database
vrm_release
15.00
category
Programming Reference
featnum
B035-1184-015K

Why Teradata Database Does Not Support The ANSI SQL STATE and RELATIVE Comparison Options

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.