oracle常用函数介绍

字符函数

数学函数

日期函数

转换函数

to_char(数字/日期)是把日期或数字转换为字符串

• 将数字转换成指定格式
• 

• to_char(1210.73, '9999.9')           -- would return '1210.7'
  to_char(1210.73, '9,999.99')      -- would return '1,210.73'
  to_char(1210.73, '$9,999.00')   --  would return '$1,210.73'
  to_char(21, '000099')           -- would return '000021'

• 将日期转换成指定格式
• 

  to_char(sysdate, 'yyyy/mm/dd');--would return '2003/07/09'
  select to_char(sysdate, 'yyyy-mm-dd  hh24:mi:ss')  from a;    ------> 2015-08-28  14:43:15
  select to_char(sysdate, 'yyyy-mm-dd  hh12:mi:ss')  from a;    ------> 2015-08-28  02:43:15
  to_char(sysdate, 'yyyy/mm/dd');--would return '2003/07/09'
  to_char(sysdate,'dd-mm-yyyy')--按dd-mm-yyyy格式转换23-05 -2016
  to_char(sysdate, 'Month DD, YYYY');--would return '10月 21, 2015'
  to_char(sysdate, 'FMMonth DD, YYYY');--would return 'July 9, 2003'
  to_char(sysdate, 'MON DDth, YYYY');--would return 'JUL 09TH, 2003'
  to_char(sysdate, 'FMMON DDth, YYYY');--would return 'JUL 9TH, 2003'
  to_char(sysdate, 'FMMon ddth, YYYY');--would return 'Jul 9th, 2003'
  to_char(sysdate, 'FMMonth DD, YYYY');--would return 'July 9, 2003'
  to_char(sysdate, 'FMMON DDth, YYYY');--would return 'JUL 9TH, 2003'
  to_char(sysdate, 'FMMon ddth, YYYY');--would return 'Jul 9th, 2003'

to_number(字符串)  将给出的字符转换为数字

select to_number('123') from a ;  

常规函数