How to cast as numeric

Hi ,

I would like to know how to cast as numeric.For examlple

I can use cast as

cast(to_number(substring(os_crm_exchange_call_id, 4), 999999999999)  as
smallint)

but here I will have the restriction of the field so If I want to cast it as
numeric how
do I do that.
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Best Regards
- Savita
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