--1.  查询工资大于12000的员工姓名和工资select first_name,last_name,salary from employees where salary > 12000--2.    查询员工号为176的员工的姓名和部门号select first_name,last_name,department_id from employees where job_id = '176'--3.    选择工资不在5000到12000的员工的姓名和工资select first_name,last_name,salary from employees where salary < 5000 and salary > 12000--4.    选择雇用时间在1998-02-01到1998-05-01之间的员工姓名，job_id和雇用时间select first_name,last_name,job_id,hire_date from employees where to_char(hire_date,'yyyy-mm-dd')>='1998-02-01' and to_char(hire_date,'yyyy-mm-dd')<='1998-05-01'; --5.    选择在20或50号部门工作的员工姓名和部门号select first_name,last_name,department_id from employees where department_id in (20,50)--6.    选择在1994年雇用的员工的姓名和雇用时间select first_name,last_name,hire_date from employees where to_char(hire_date,'yyyy')='1994'--7.    选择公司中没有管理者的员工姓名及job_idselect first_name,last_name,job_id from employees where manager_id is null;--8.    选择公司中有奖金的员工姓名，工资和奖金级别select first_name,last_name,salary,commission_pct from employees where commission_pct is not null --9.    选择员工姓名的第三个字母是a的员工姓名select first_name,last_name from employees where first_name like '__a%' or last_name like '__a%';--10.    选择姓名中有字母a和e的员工姓名select first_name,last_name from employees where  lower(first_name) like '%a%'and lower(first_name) like '%e%' or lower(last_name)like '%a%' and lower(last_name)like '%e%';--单行函数--1.    显示系统时间(注：日期+时间)select sysdate from dual--2.    查询员工号，姓名，工资，以及工资提高百分之20%后的结果（new salary）select employee_id,first_name,last_name,salary,salary*1.2 as "NEW SALARY" from employees--3.    将员工的姓名按首字母排序，并写出姓名的长度（length）select  substr(first_name,1,1) as FIRSTWORD, length(first_name) as "LENGTH" from employees order by substr(first_name,1,1) asc--4.    查询各员工的姓名，并显示出各员工在公司工作的月份数（worked_month）。select first_name,last_name,round( months_between(sysdate,hire_date))WORKED_MONTHS from employees--5.    查询员工的姓名，以及在公司工作的月份数（worked_month），并按月份数降序排列select first_name,last_name,round( months_between(sysdate,hire_date))WORKED_MONTHS from employees order by WORKED_MONTHS desc /*6.    做一个查询，产生下面的结果
     
       earns 
      
        monthly but wants 
       
        Dream SalaryKing earns $24000 monthly but wants $72000*/select last_name || ' earns '||salary||' monthly but wants '||salary*3 as "A GREAT DREAM" from employees/*7.    使用decode函数，按照下面的条件：job                  gradeAD_PRES            AST_MAN             BIT_PROG             CSA_REP              DST_CLERK           E产生下面的结果Last_name    Job_id    Gradeking    AD_PRES    A*/select Last_name||' '||job_id||' '||decode(job_id,'AD_PRES','A',                                                  'ST_MAN','B',                                                  'IT_PROG','C',                                                  'SA_REP','D',                                                  'ST_CLERK','E') ||' king    AD_PRES    A' as SOMEWORDS from employees--8.    将第7题的查询用case函数再写一遍。select Last_name||' '||job_id||' '||case job_id when 'AD_PRES' then 'A'                                                when 'ST_MAN' then 'B'                                                when 'IT_PROG' then 'C'                                                when 'SA_REP' then 'D'                                                when 'ST_CLERK' then 'E'                                                else ' '                                                end ||' king    AD_PRES    A' as SOMEWORDS from employees