单项选择题
A. Removes the table
B. Removes all rows from a table
C. Shortens the table to 10 rows
D. Removes all columns from a table
E. Removes foreign keys from a table
单项选择题 Which is an /SQL*Plus command?（）
单项选择题 Examine the data of the EMPLOYEES table. EMPLOYEES (EMPLOYEE_ID is the primary key. MGR_ID is the ID of managers and refers to the EMPLOYEE_ID) Evaluate this SQL statement: What is its output?（）
单项选择题 Which SELECT statement should you use to extract the year from the system date and display it in the format "1998"?（）