Conversion function of Oracle single-line function

To_char (string \ column, format string): Turns a date or number into a string display

Note: The time string or the time type column and the format string must be one by one corresponding, if more than the relevant characters will be error (in addition to using Systemdate, because To_char (System, ' YYYY-MM-DD ') This will not be an error)

If you precede the format string with FM and ' FMYYYY-MM-DD ', you will reject 0 in mm, and the case 2017-03-20 becomes 2017-3-20

To_date (string \ column, format string): Turns a string into a Date data display

To_number (String \ Column): Turns a string into a digital display

Conversion function of Oracle single-line function