欢迎进入Oracle社区论坛，与200万技术人员互动交流 >>进入 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. selec欢迎进入oracle社区论坛，与200万技术人员互动交流 >>进入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;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) 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 oracle知识库oracle知识库下载下载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 语句中用来连接字符串的符号是______.
A. “+” B. “&” C.“||” D.“|”
问答题： 什么是聚集索引，什么是非聚集索引，什么又是主键？