Purpose:Wraps an immutable value for a past time. A session, query, or expression can be as of a past time.
For Oracle 9R2 Flasback corresponds to the sub clause which appears between the table and alias name in the FROM clause: SELECT ... FROM EMPLOYEE AS OF TIMESTAMP (value) t0, ...
For generic historical schema support, a special criteria can be added to the where clause for each table in a select: ((t0.ROW_START <= value) AND ((t0.END IS NULL) OR (t1.END> value)))
Responsibilities: - By default AsOfClause is a timestamp. To specify a system change number use AsOfSCNClause.
- For Oracle 9R2 Flashback prints the correct AS OF clause before the alias name in the FROM clause.
- Read-only: the wrapped value can not change.
@since OracleAS TopLink 10g (10.0.3)
@author Stephen McRitchie
@see org.eclipse.persistence.expressions.Expression#asOf(AsOfClause)
@see org.eclipse.persistence.queries.ObjectLevelReadQuery#asOf(AsOfClause)
@see org.eclipse.persistence.sessions.Session#acquireSessionAsOf(AsOfClause)
@see HistoryPolicy