单项选择题
A.The indexed column is declared as NOT NULL.
B.The indexed columns are used in the FROM clause.
C.The indexed columns are part of an expression.
D.The indexed column contains a wide range of values.
单项选择题 A subquery can be used to（）.
单项选择题 Click the Exhibit button to examine the data of the EMPLOYEES table. Evaluate this SQL statement: SELECT e.employee_id "Emp_id", e.emp_name "Employee", e.salary, m.employee_id "Mgr_id", m.emp_name "Manager" FROM employees e JOIN employees m ON (e.mgr_id = m.employee_id) AND e.salary > 4000; What is its output?（）
多项选择题 For which two actions can you use the TO_DATE function? （）