Function Description
Oracle function TO_NUMBER returns argument x in NUMBER datatype. Optional input arguments are Oracle format elements and nls language.
Here you will find Oracle format elements with examples.
Examples
SELECT TO_NUMBER('555')
  FROM dual; 
Result: 555
SELECT TO_NUMBER('555.12')
  FROM dual; 
Result: 555.12
SELECT TO_NUMBER('-555.00', 'FM999.99')
  FROM dual;
Result: -555