单项选择题
A. Create groups of data
B. Sort data in a specific order
C. Convert data to a different format
D. Retrieve data based on an unknown condition
单项选择题 Which clause should you use to exclude group results?（）
单项选择题 Evaluate these two SQL statements:SELECT last_name, salary, hire_dateFROM EMPLOYEES ORDRE BY salary DESC; SELECT last_name, salary, hire_dateFROM EMPOLYEES ORDER BY 2 DESC; What is true about them?（）
单项选择题 Which is an iSQL*Plus command?（）