多项选择题
A. When a table is dropped， the corresponding indexes are automatically dropped.
B. For each DML operation performed， the corresponding indexes are automatically updated.
C. Indexes should be created on columns that are frequently referenced as part of an expression.
D. A non-deferrable PRIMARY KEY or UNIQUE KEY constraint in a table automatically creates a uniqueindex.
单项选择题 Evaluate the following SQL statements that are issued in the given order： What would be the status of the foreign key EMP_MGR_FK？（）
单项选择题 WhichstatementistrueregardingFlashbackVersionQuery？（）
单项选择题 View the Exhibit and examine the structure of the EMP table. You executed the following command to add a primary key to the EMP table： ALTER TABLE emp ADD CONSTRAINT emp_id_pk PRIMARY KEY （emp_id） USING INDEX emp_id_idx； Which statement is true regarding the effect of the command？（）