SQL Decode format numbers only - sql

Question

I want to format amounts to salary format, e.g. 10000 becomes 10,000, so I use to_char(amount, '99,999,99')
SELECT SUM(DECODE(e.element_name,'Basic Salary',to_char(v.screen_entry_value,'99,999,99'),0)) Salary,
SUM(DECODE(e.element_name,'Transportation Allowance',to_char(v.screen_entry_value,'99,999,99'),0)) Transportation,
SUM(DECODE(e.element_name,'GOSI Processing',to_char(v.screen_entry_value,'99,999,99'),0)) GOSI,
SUM(DECODE(e.element_name,'Housing Allowance',to_char(v.screen_entry_value,'99,999,99'),0)) Housing
FROM values v,
values_types vt,
elements e
WHERE vt.value_type = 'Amount'
this gives error invalid number because not all values are numbers until value_type is equal to Amount but I guess decode check all values anyway although what I know is that the execution begins with from then where then select, what's going wrong here?

Answer 1

You said you added decode(...), but it looks like you might have actually added sum(decode(...)).
You are converting your values to strings with to_char(v.screen_entry_value,'99,999,99'), so your decode() generates a string - the default 0 will be converted to '0' - giving you a value like '1,234,56'. Then you are aggregating those, so sum() has to implicitly convert those strings to numbers - and it is throwing the error when it tries to do that:
select to_number('1,234,56') from dual
will also get "ORA-01722: invalid number", unless you supply a similar format mask so it knows how to interpret it. You could do that, e.g.:
SUM(to_number(DECODE(e.element_name,'Basic Salary',to_char(v.screen_entry_value,'99,999,99'),0),'99,999,99'))
... but it's maybe more obvious that something is strange, and even if you did, you would end up with a number, not a formatted string.
So instead of doing:
SUM(DECODE(e.element_name,'Basic Salary',to_char(v.screen_entry_value,'99,999,99'),0))
you should format the result after aggregating:
to_char(SUM(DECODE(e.element_name,'Basic Salary',v.screen_entry_value,0)),'99,999,99')
fiddle with dummy tables, data and joins.