PL/SQL How to implement conditional select - select

Question

I have a small problem which I believed I could solve simply, it turns out I'm not able to figure out.
I have following query:
SELECT custom_field
INTO v_start_of_invoice
FROM BILL
WHERE BIMA_TRACKING_ID = v_previous_BIMAtrackingID
AND BSCO_CODE_ID = 'PRPAYMENT'
AND PREP_SEQ_NUM = 0
AND ITEM_CAT_CODE_ID = 1
AND PARTITION_KEY = v_prev_partition
AND SUBPARTITION_KEY = v_prev_subpartition;
What I would like to achieve here is to give to variable v_start_of_invoice the value "0" if one or all the where condition are not met.
In simple word I don't want the script to fail but I want the variable either to be set with some value if all the where conditions are matched, otherwise I want to assign the value 0.
I'm sure there are quite a few ways but I need to check what could be the best way to achieve that.
Many Thks in advance
M.

Answer 1

You seem to have a misunderstanding of what the exception block actually does. First off you cannot avoid the exception. If you use "select into" the query is successful only when exactly 1 row is returned. Otherwise PLSQL will internally raise the NO_DATA_FOUND when the query returns 0 rows, and TOO_MANY_ROWS when it returns more then 1 row. The exception block tells PLSQL what to do when an error is generated. Basically the exception block tells what action to take on specific errors and whether to continue error processing or discard the error. (Check the RAISE and RAISE_APPLICATION_ERROR statements.)
Keep in mind that blocks can be nested. With this in mind and in context of a outer block the solution offered by #are is exactly what you want. The structure becomes:
Begin
.
.
.
begin
place #are's code here.
end ;
-- Continue your code here: The Error has been handled and execution continues as though the exception never happened.
.
.
.
end;
As far as the "NVL(v_start_of_invoice, 0);" it's a function that will return 0 if v_start_of_invoice is NULL and v_start_of_invoice otherwise. Note the value of INTO variables is not it the select generates an error unless you set it in the exception block.

Answer 2

begin
SELECT custom_field
INTO v_start_of_invoice
FROM BILL
WHERE BIMA_TRACKING_ID = v_previous_BIMAtrackingID
AND BSCO_CODE_ID = 'PRPAYMENT'
AND PREP_SEQ_NUM = 0
AND ITEM_CAT_CODE_ID = 1
AND PARTITION_KEY = v_prev_partition
AND SUBPARTITION_KEY = v_prev_subpartition;
exception WHEN NO_DATA_FOUND THEN
v_start_of_invoice := 0;
end;