1)description of the students table:

sid_id number

start_date date

end_date date

which two function are valid on the start_date column?_________。

a. sum(start_date)

b. avg(start_date)

c. count(start_date)

d. avg(start_date,end_date)

e. min(start_date)

f. maximum(start_date)

2)which statement shows the maximum salary paid in each job category of each department?_______

a. select dept_id, job_cat,max(salary) from employees where salary > max(salary);

b. select dept_id, job_cat,max(salary) from employees group by dept_id,job_cat;

c. select dept_id, job_cat,max(salary) from employees;

d. select dept_id, job_cat,max(salary) from employees group by dept_id;

e. select dept_id, job_cat,max(salary) from employees group by dept_id,job_cat,salary;

3)for which two constraints does the oracle server implicitly create a unique index?______。

a. not null

b. primary

c. foreign key

d. check

e. unique

4)in a select statement that includes a where clause,where is the group by clause placed in the select statement?______。

a. immediately after the select clause

b. before the where clause

c. before the from clause

d. after the order by clause

e. after the where clause

5)in a select statement that includes a where clause,where is the order by clause placed in the select statement?______.

a.immediately after the select clause

b.before the where clause

c.after all clause

d.after the where clause

e.before the from clause

6)evaluate there two sql statements______.

select last_name,salary from employees order by salary;

select last_name,salary from employees order by 2 asc;

a.the same result b.different result c.the second statement returns a syntax error

7) you would like to display the system date in the format“20051110 14：44：17”。which select statement should you use?______。

a. select to_date(sydate,’yearmmdd hh:mm:ss’)from dual;

b. select to_char(sydate,’yearmonthday hh:mi:ss’)from dual;

c. select to_date(sydate,’yyyymmdd hh24:mi:ss’)from dual;

d. select to_char(sydate,’yyyymmdd hh24:mi:ss’)from dual;

e. select to_char(sydate,’yy-mm-dd hh24:mi:ss’)from dual;

8)which select statement will the result ‘ello world’from the string‘hello world’?______.

a. select substr(‘hello world’,1)from dual;

b. select substr(trim(‘hello world’,1,1))from dual;

c. select lower(substr(‘hello world’,1))from dual;

d. select lower(trim(‘h’from‘hello world’))from dual;

9)which are dml statements(choose all that apply)______.

a.commit b.merge c.update d.delete e.creat f.drop

10)select 語句中用來連接字符串的符號是___c___.

a. “+” b. “&” c.“||” d.“|”

問答題： 什么是聚集索引，什么是非聚集索引，什么又是主鍵?