Dynamic length on number format in to_number Oracle SQL

问题

I have a table with numbers stored as varchar2 with '.' as decimal separator (e.g. '5.92843').

I want to calculate with these numbers using ',' as that is the system default and have used the following to_number to do this:

TO_NUMBER(number,'99999D9999','NLS_NUMERIC_CHARACTERS = ''.,''')

My problem is that some numbers can be very long, as the field is VARCHAR2(100), and when it is longer than my defined format, my to_number fails with a ORA-01722.

Is there any way I can define a dynamic number format? I do not really care about the format as long as I can set my decimal character.

回答1:

Is there any way I can define an unlimited number format?

The only way, is to set the appropriate value for nls_numeric_characters parameter session wide and use to_number() function without specifying a format mask.

Here is a simple example.Decimal separator character is comma "," and numeric literals contain period "." as decimal separator character:

SQL> show parameter nls_numeric_characters;

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------
nls_numeric_characters               string      ,.

SQL> with t1(col) as(
  2    select '12345.567'  from dual union all
  3    select '12.45'      from dual
  4  )
  5  select to_number(col) as res
  6    from t1;
select to_number(col)
       *
ERROR at line 5:
ORA-01722: invalid number 

SQL> alter session set nls_numeric_characters='.,';

Session altered.

SQL> with t1(col) as(
  2    select '12345.567'  from dual union all
  3    select '12.45'      from dual
  4  )
  5  select to_number(col) as res
  6    from t1;

res                                                                 
--------------    
     12345.567       
         12.45

回答2:

You can't have "unlimited" number. Maximum precision is 38 significant digits. From the documentation.

回答3:

You might try one of the following approaches (take them for an idea as I do not have a DB for trying it here):

1) Use TO_NUMBER without a format. According to Oracle docs it uses a dot for decimal separator then.

If your number contains group separators, then first remove these and convert then:

TO_NUMBER(TRANSLATE(number, ',''' ,''))

2) Generate the number format from your input:

select TO_NUMBER(n, TRANSLATE(n,' 1,234.567890',TO_CHAR(9999.9, '9G999D9')||'99999'))
from (select '9,876.54' as n from dual);

The latter translates all digits to 9, your group character (here: comma) and your decimal separator (here: dot) to those used by Oracle by default.

来源：https://stackoverflow.com/questions/20196816/dynamic-length-on-number-format-in-to-number-oracle-sql

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Oracle

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