How to replace with zero after full-stop if not have any value using regexp_substr in oracle - oracle11g

Question

Values are like:
Num(column)
786.56
35
select num,regexp_substr(num,'[^.]*') "first",regexp_substr(num,'[^.]+$') "second" from cost
when i execute the above query output will be like
num first second
786.56 786 56
35 35 35
I want to print zero if not have any value after full-stop,by default second column repeating first value

Answer 1

There are two options here; using either the occurrence or subexpression parameters available in REGEXP_SUBSTR().
Subexpression - the 5th parameter
Using subexpressions you can pick out which group () in your match you want to return in any given function call
SQL> with the_data (n) as (
2 select 786.56 from dual union all
3 select 35 from dual
4 )
5 select regexp_substr(n, '^(\d+)\.?(\d+)?$', 1, 1, null, 1) as f
6 , regexp_substr(n, '^(\d+)\.?(\d+)?$', 1, 1, null, 2) as s
7 from the_data;
F S
--- ---
786 56
35
^(\d+)\.?(\d+)?$ means at the start of the string ^, pick a group () of digits \d+ followed by an optional \.?. Then, pick an optional group of digits at the end of the string $.
We then use sub-expressions to pick out which group of digits you want to return.
Occurrence - the 3th parameter
If you place the number in a group and forget about matching the start and end of the string you can pick the first group of numbers and the second group of numbers:
SQL> with the_data (n) as (
2 select 786.56 from dual union all
3 select 35 from dual
4 )
5 select regexp_substr(n, '(\d+)\.?', 1, 1, null, 1) as f
6 , regexp_substr(n, '(\d+)\.?', 1, 2, null, 1) as s
7 from the_data;
F S
--- ---
786 56
35
(\d+)\.? means pick a group () of digits \d+ followed by an optional .. For the first group the first occurrence is the data before the ., for the second group the second occurrence is the data after .. You'll note that you still have to use the 5th parameter of REGEXP_SUBSTR() - subexpression - to state that you want the only the data in the group.
Both options
You'll note that neither of these return 0 when there are no decimal places; you'll have to add that in with a COALESCE() when the return value is NULL. You also need an explicit cast to an integer as COALESCE() expects consistent data types (this is best practice anyway):
SQL> with the_data (n) as (
2 select 786.56 from dual union all
3 select 35 from dual
4 )
5 select cast(regexp_substr(n, '^(\d+)\.?(\d+)?$', 1, 1, null, 1) as integer) as f
6 , coalesce(cast(regexp_substr(n, '^(\d+)\.?(\d+)?$', 1, 1, null, 2) as integer), 0) as s
7 from the_data;
F S
---- ----
786 56
35 0