第 56 题 (多选题)： Which three statements are true about Private Temporary Tables (PTTs)in an Oracle Database.

A. Concurrent sessions may have PTTs with the same name but different column definitions . B. Concurrent sessions may have PTTs with the same name and the same column definitions . C. Creating a PTT is DDL and commits any active transaction for the session. D. It is possible to preserve the private table definition but remove the rows when a session with a PTT issues a COMMIT. E. Concurrent sessions may have PTTs with different names but same column definitions 显示答案