当水位达到设防水位后继续上升到某一水位时，防洪堤随时可能出险，此时的水位称为（） 危险水位。 防汛水位。 警戒水位。 保证水位。
The（）writes the Flashback Database logs in the flash recovery area. FLSH。 FLDB。 RVWR。 RVRW。 FBDA。
Examine the structure of the EMPLOYEES table: EMPLOYEE_ID NUMBER Primary Key FIRST_NAME VARCHAR2 (25) LAST_NAME VARCHAR2 (25) HIRE_DATE DATE Which UPDATE statement is valid? （） UPDATE employees SET first_name = 'John' SET last_name = 'Smith' WHERE employee_id = 180;。 UPDATE employees SET first_name = 'John', SET last_name = 'Smoth' WHERE employee_id = 180;。 UPDATE employee SET first_name = 'John' AND last_name = 'Smith' WHERE employee_id = 180;。 UPDATE employee SET first_name = 'John', last_name = 'Smith' WHERE employee_id = 180。
You executed the following query： SELECT operation， undo_sql， table_name FROM flashback_transaction_query; Which statement is correct regarding the query output？（） It would return information regarding only the last committed transaction.。 It would return only the active transactions in all the undo segments in the database.。 It would return only the committed transactions in all the undo segments in the database. 。 It would return both active and committed transactions in all the undo segments in the database.。 It would return information regarding the transactions that began and were committed in the last 30 minutes.。
简述鲜花加工工具及用途。
生产过程的出发点是（）。
