单项选择题
A. Substitution variables
B. Replacement variables
C. Prompt variables
D. Instead-of variables
E. This feature cannot be implemented through /SQL*Plus
单项选择题 Examine the description of the MARKS table: SUBJ1 and SUBJ2 indicate the marks obtained by a student in two subjects. Examine this SELECT statement based on the MARKS table: What is the result of the SELECT statement?（）
单项选择题 Evaluate the SQL statement: What will be displayed?（）
单项选择题 The EMP table contains these columns: You need to display the employees who have not been assigned to any department. You write the SELECT statement: What is true about this SQL statement?（）