多项选择题 Which two statements are true about constraints? （）

多项选择题 Evaluate the SQL statement:TRUNCATE TABLE DEPT;Which three are true about the SQL statement? （）

单项选择题 You need to perform certain data manipulation operations through a view called EMP_DEPT_VU, which you previously created. You want to look at the definition of the view (the SELECT statement on which the view was create.) How do you obtain the definition of the view?（）