选择题：
神州数码笔试1)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;
神州数码笔试2)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)
神州数码笔试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
神州数码笔试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
神州数码笔试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
神州数码笔试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
神州数码笔试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;
神州数码笔试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;
神州数码笔试9)which are dml statements(choose all that apply)______。
a。commit b。merge c。update d。delete e。creat f。drop
神州数码笔试10)select 语句中用来连接字符串的符号是___c___。