单项选择题
In which scenario would index be most useful?（）
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.
多项选择题 Which two are true about aggregate functions?（）
多项选择题 Which two are attributes of iSQL*Plus? （）
单项选择题 Examine the structure if the EMPLOYEES and NEW EMPLOYEES tables: Which MERGE statement is valid?（）
