16.10 - About Session Modes and Transaction Processing - Teradata Database

Teradata Database Administration

Product
Teradata Database
Release Number
16.10
Release Date
April 2018
Content Type
Administration
Publication ID
B035-1093-161K
Language
English (United States)

Teradata Database supports two session modes:

  • ANSI
  • Teradata

In ANSI session mode:

  • Transaction processing follows the rules defined by the ANSI/ISO SQL:2011 standard.
  • For Teradata SQL features that support both the ANSI/ISO SQL standard syntax and the Teradata SQL dialect, the ANSI/ISO SQL standard syntax is used.
  • The default case specification for character data is CASESPECIFIC.
  • When a character string requires truncation, the excess pad characters are truncated without reporting an error. Truncation of characters other than trailing nonblank characters results in a truncation exception.
  • Cursors are always positioned. Updating or deleting the most current fetched cursor row using the UPDATE/DELETE … WHERE CURRENT OF statement is valid.
  • The default table type is MULTISET, which allows duplicate rows.
  • The TRIM function trims both leading and trailing pad characters by default.

In Teradata session mode:

  • Transaction processing follows the rules defined by Teradata before the emergence of the ANSI/ISO SQL standard. These rules largely conform with ANSI/ISO semantics, but in some cases differ in important ways from the ANSI/ISO semantics.
  • For Teradata SQL features that support both the ANSI/ISO SQL standard syntax and the Teradata SQL dialect, the Teradata SQL syntax is used.
  • By default, character data is NOT CASESPECIFIC, except when the character set is GRAPHIC. GRAPHIC character data by default is CASESPECIFIC.
  • The default case specification for character data is NOT CASESPECIFIC. The exception is data of type CHARACTER (n) CHARACTER SET GRAPHIC, which is always CASESPECIFIC.
  • When a character string requires truncation, the string is truncated silently with no truncation notification given. This is true for truncation of pad or non-pad characters.
  • Cursors are never positioned. Updating or deleting the most current fetched cursor row using the UPDATE/DELETE … WHERE CURRENT OF statement is not valid.
  • The default table type depends on whether the table has a primary index. Tables with a PI are SET (do not allow duplicate rows). Tables without a primary index (including column-partitioned tables) are MULTISET (allow duplicate rows).
  • The TRIM function trims only trailing pad characters by default.
Case specificity does not apply to CLOBs.

A transaction is a logical unit of work. The statements nested within the transaction either execute successfully as a group or do not execute. A Teradata SQL transaction can be a single Teradata SQL statement, or a sequence of Teradata SQL statements.