1Z0-060 全真模擬試験 DEMO

問題20: You create a table with the PERIOD FOR clause to enable the use of the Temporal Validity
feature of Oracle Database 12c.
Examine the table definition:
Which three statements are true concerning the use of the Valid Time Temporal feature for the
EMPLOYEES table? (Choose three.)
A. The valid time columns are visible by default when the table is described.
B. The valid time columns are not populated by the Oracle Server automatically.
C. The same statement may filter on both transaction time and valid temporal time by using the AS
OF TIMESTAMP and PERIOD FOR clauses.
D. Setting the session valid time using DBMS_FLASHBACK_ARCHIVENABLE_AT_VALID_TIME sets the
visibility for data manipulation language (DML), data definition language (DDL), and queries
performed by the session.
E. The valid time columns employee_time_start and employee_time_end are automatically created.
正解: C,D,E
Explanation
A: To implement Temporal Validity(TV), 12c offers the option to have two date columns in that table
which is having TV enabled using the new clause Period For in the Create Table for the newly created
tables or in the Alter Table for the existing ones. The columns that are used can be defined while
creating the table itself and will be used in the Period For clause or you can skip having them in the
table's definition in the case of which, the Period For clause would be creating them internally.
E: ENABLE_AT_VALID_TIME Procedure
This procedure enables session level valid time flashback.