如何获得 Oracle 中长数字的准确长度

Question

I'm working with a schema (not created by me) that has calculated variances that can be really long numbers. I need to identify these long numbers so I can trunc them. The problem is that they are so long, the length function doesn't seem to recognize them as being long.

SELECT Length(10.00000000000000000000000000000000000004) FROM dual;

result: 2

Obviously the number above is longer than 2 digits, but the length function doesn't recognize this. How do I get an accurate length of this number, so I can find all the cases where they exist?

Answer 1

This happens because the length() function accepts a string as input, not a number, so the value is implicitly converted to a string using some default format before the function ever sees it.

There may be a more elegant mathematical solution, but one approach would be to use the 'text minimum' number format , length(to_char(num,'TM')) :

with demo(num) as (select 10.00000000000000000000000000000000000004 from dual)
select to_char(num)
     , to_char(num,'TM')
     , length(to_char(num,'TM'))
from   demo;

TO_CHAR(NUM)  TO_CHAR(NUM,'TM')                         LENGTH(TO_CHAR(NUM,'TM'))
------------- ----------------------------------------- -------------------------
10            10.00000000000000000000000000000000000004                        41