吉大20春学期《数据库应用技术》在线作业一-0003
试卷总分:100
一、单选题(共25 道试题,共100 分)
1.如果选用循环日志方式，辅助日志文件何时分配？
A.数据库建立的时候
B.数据库服务器启动的时候
C.需要的时候
D.以上都不对
正确答案:C
2.Given the following table: CREATE TABLE employee (name CHAR(10), salary DEC NOT NULL WITH DEFAULT) INSERT INTO employee (name, salary) V ALUES ('SMITH', 30000) INSERT INTO employee (name) V ALUES ('JONES') INSERT INTO employee (name, salary) V ALUES ('ALI', 35000) Which of the following statements will retrieve more than one row?
A.SELECT salary FROM employee WHERE salary IN (SELECT (salary/(SELECT SUM(salary) FROM employee)) FROM employee)
B.SELECT COALESCE(A VG(salary)) FROM employee
C.SELECT SUM(salary)/COUNT(*) FROM employee
D.SELECT salary/(SELECT SUM(salary) FROM employee) FROM employee
正确答案:D
3.据库系统和文件系统的主要区别是：。