Linux课堂随笔--第十一天

Posted 2020-09-30

排序：

SQL> select last_name, salary from employees order by salary;

SQL> select last_name, salary from employees order by salary desc;大到小

SQL> select last_name, salary from employees order by last_name;

SQL> select last_name, hire_date from employees order by hire_date;

SQL> select last_name, salary, commission_pct from employees order by salary desc, commission_pct desc;

SQL> select last_name, salary*12*(1+commission_pct) from employees order by 2;

SQL> select last_name, salary*12*(1+commission_pct) total_salary from employees order by total_salary;

单行函数

SQL> select upper(first_name), lower(last_name), length(last_name) from employees;

 

SQL> select (sysdate-hire_date)/7 from employees;

SQL> select trunc((sysdate-hire_date)/30, 0) from employees;

SQL> select trunc(months_between(sysdate,hire_date), 0) from employees;

SQL> select sysdate+3650 from dual;

SQL> select add_months(sysdate, 120) from dual;

SQL> select next_day(‘2015-09-01‘, ‘friday‘) from dual;

SQL> select next_day(‘2015-10-01‘, 6) from dual;

SQL> select last_day(sysdate) from dual;

 

SQL> select round(to_date(‘2015-10-10‘,‘yyyy-mm-dd‘), ‘MONTH‘) from dual;

SQL> select round(to_date(‘2015-10-16‘,‘yyyy-mm-dd‘), ‘MONTH‘) from dual;

SQL> select round(to_date(‘2015-10-10‘,‘yyyy-mm-dd‘), ‘YEAR‘) from dual;

SQL> select round(sysdate, ‘DAY‘) from dual;

 

 

类型转换和其他函,数

转换   to_char

SQL> select to_char(salary, ‘$999,999.00‘) from employees;

SQL> select last_name, to_char(hire_date, ‘dd-Mon-RR‘) from employees;

SQL> select to_char(sysdate, ‘yyyy-mm-dd hh24:mi:ss‘) from dual;

SQL> select to_char(sysdate, ‘yyyy-mm-dd hh:mi:ss AM‘) from dual;

SQL> select last_name from employees where hire_date=to_date(‘2006-05-23‘, ‘yyyy-mm-dd‘);

SQL> select to_number(‘$123,456.78‘, ‘$999,999.00‘) from dual;

 

 

一

elect last_name, job_id, salary,

case job_id

  when ‘IT_PROG‘ then salary+1000

  when ‘SA_REP‘ then salary+1500

  when ‘ST_CLERK‘ then salary+2000

  else salary

end new_salary

from employees;

二 

select last_name, job_id, salary,

decode( job_id,

  ‘IT_PROG‘, salary+1000,

  ‘SA_REP‘,  salary+1500,

  ‘ST_CLERK‘, salary+2000,

  salary) new_salary

from employees;