The problem of time conversion in oracle

Http://www.cnblogs.com/hanyun/archive/2009/05/14/1456772.html

1)。 When using Oracle's to_date function for date conversion, you may intuitively use the format "yyyy-MM-dd HH:mm:ss" as the format for conversion, but it will cause an error in Oracle: "the ORA 01810 format code appears twice." For example: select to_date ('2005-01-01 13-14-14-20-15-12-12-13-14-13-14-15-12-12-12-12-12-12-14-14-13-14-13-14-13-14-14-13-14-14-20-12-12-12-12-12-12-12-12-12-12-12-12-14-14-14-14-12-14-14-14-12-12-12-12-12-12-12-14-14-14-12-14-14-12-14-14-13-14-14-13-14-14-13-14-14-13-14-14-13-14-14-13-14-12-14-14-12-14-14-13-14-13-14-14

The reason is that SQL is case-insensitive, MM and mm are considered to be the same format code, so Oracle's SQL uses mi instead of minutes. Select to_date ('2005-01-01 13-14-14-20-13-14-14-20) from dual

2)。 In addition, it needs to be displayed in a 24-hour form using HH24.

Select to_char (sysdate,'yyyy-MM-dd HH24:mi:ss') from dual;//mi is minutes

Select to_char (sysdate,'yyyy-MM-dd HH24:mm:ss') from dual;//mm displays the month