Question

I’m having trouble with TO_NUMBER function second and third parameters. Does one of them depend on the other one? How does nls_params parameter work? I can’t understand how the the result of the query

SELECT TO_NUMBER('17.000,23', 
             '999G999D99', 
             'nls_numeric_characters='',.'' ')  
             REFORMATTED_NUMBER 
FROM   DUAL; 

can be 17000.23. Could somebody please explain the process of the above conversion.

P.S. The above query is taken from an Oracle Database SQL Expert Certificate preparation book.

Answer 1

Now, I’ll answer my own question. While using TO_NUMBER function I missed the important point that, whatever I get from TO_NUMBER function is going to be a number. And a number does not include anything else than decimal point and E scientific notation. So 17,788.99 is not actually a number but is rather the string representation of 17788.99.

If we try to subtract 500 from 17,788.99 we’ll fail.(Well, Oracle implicitly converts numeric strings to numbers and vice-versa, but principally we can’t perform arithmetic operations between strings and numbers). I’m sure that TO_NUMBER function is almost never used to select a column value. It’s rather used to be able to make arithmetic operations. Instead, we use TO_CHAR to show a column value or any numeric expression in a neat, easy to read format. The fomat models and nls_params are not only for TO_NUMBER function, but for TO_CHAR as well.