17.10 - As Of Query - Advanced SQL Engine - Teradata Database

Teradata Vantage™ - Temporal Table Support

Product
Advanced SQL Engine
Teradata Database
Release Number
17.10
Release Date
July 2021
Content Type
Programming Reference
Publication ID
B035-1182-171K
Language
English (United States)

An as of query is a SELECT statement that extracts and operates on rows in temporal tables with valid-time and transaction-time periods that overlap an AS OF date or time specified in the query. As of queries operate on the data as a snapshot at any point in time. Typically, as of queries are used for querying historical data.

The AS OF clause can be applied to the valid-time and transaction-time dimensions together or independently. When applied to the valid-time dimension, it retrieves rows where the PV overlaps the specified AS OF time. When applied to the transaction-time dimension, it retrieves rows with transaction-time periods that overlap the specified AS OF time.

An as of query is similar in semantics to a current query; an AS OF extracts the information based on the specified time and a current query extracts the information as of the current time or date of the query being executed. However, a current query operates on only open rows in the transaction-time dimension. An AS OF query can read rows as of a particular point in time in the transaction-time dimension regardless of whether the rows are closed or open.

An as of query produces a nontemporal table as a result set.