多项选择题
What are two reasons to create synonyms?（）
A. You have too many tables. B. Your tables are too long. C. Your tables have difficult names. D. You want to work on your own tables. E. You want to use another schema's tables. F. You have too many columns in your tables.
多项选择题 Which three statements about subqueries are true?（）
单项选择题 Which SQL statement returns a numeric value?（）
多项选择题 When should you create a role?（）
