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.