Performing select operations with a cursor inside a caught exception - plsql

Question

I'm trying to write a Stored Procedure which takes input of an ID then searches 3 different tables for that item using different criteria. One solution I have is to perform the select statement on each table one by one, and catching the NO_DATA_FOUND exception if nothing is found via the select.
In pseudocode:
Select item from from first table
If no data found, throw exception.
Handle exception by selecting data from second table
If no data found, throw another exception.
Handle exception by selecting data from third table (if the data is not present in any row it should return 0 rows)
Here's what I have:
OPEN REQUEST FOR
SELECT REQ_TYPE, REQ_TYPE_STATUS FROM TABLEONE
WHERE TABLEONE.REQ_ID = REQUESTID
AND (REQ_STATUS = 'D' OR REQ_STATUS = 'A');
EXCEPTION WHEN NO_DATA_FOUND THEN
BEGIN
OPEN REQUEST FOR
SELECT REQ_TYPE, '-' AS REQ_TYPE_STATUS FROM TABLETWO
WHERE TABLETWO.REQ_ID = REQUESTID;
EXCEPTION WHEN NO_DATA_FOUND THEN
begin
OPEN REQUEST FOR
SELECT REQ_TYPE, '-' as REQ_TYPE_STATUS FROM THIRDTABLE
WHERE THIRDTABLE.REQ_ID = REQUESTID;
end;
END;
If an item is found in TABLEONE, it successfully returns the data for it. However, the SELECT operations that are performed inside the caught exceptions don't seem to run as the the stored procedure doesn't return any rows.
I have separately verified that the data I'm searching for definitely exists in TABLETWO AND/OR TABLETHREE.
The syntax is valid as it compiles, it's just that it doesn't return any rows if the item doesn't exist in TABLEONE (but exists in either TABLETWO or TABLETHREE).
Any ideas?

Answer 1

Credit to #Franek for this.
The referenced linked article explains the following:
Cursor FOR loop is smart. It won't raise NO-DATA-FOUND as it is; if
there's nothing to be fetched, it will exit the loop and terminate
execution successfully. Therefore, if you meant to handle it as an
EXCEPTION - you can not.
What I was attempting to do is apparently not possible. Therefore, I have implemented it this way instead:
Pseudocode:
Search for the item in the first table
If item was found
select the details of it from the first table
If item was not found
search for the item in the second table
If Item was found
Select the details of it from the second table
If item was not found
Select the item from the third table (returning blank if it's not found here neither)
PL/SQL Implementation:
-- Search for the request ID in the first table
SELECT COUNT(REQ_ID) INTO requestFound FROM FIRSTTABLE
WHERE FIRSTTABLE.REQ_ID = REQUESTID
AND (REQ_STATUS = 'D' OR REQ_STATUS = 'A');
IF(REQUESTFOUND > 0) THEN
-- Select the request details
OPEN REQUEST FOR
SELECT REQ_ID, REQ_TYPE_STATUS FROM FIRSTTABLE
WHERE FIRSTTABLE.REQ_ID = REQUESTID
AND (REQ_STATUS = 'D' OR REQ_STATUS = 'A');
ELSE
-- Search for the request from the second table
SELECT COUNT(REQ_ID) INTO REQUESTFOUND FROM SECONDTABLE
WHERE SECONDTABLE.REQ_ID = REQUESTID;
IF(REQUESTFOUND > 0) THEN
-- Select the request details from second table
OPEN REQUEST FOR
SELECT REQ_TYPE, '-' AS REQ_TYPE_STATUS FROM SECONDTABLE
WHERE SECONDTABLE.REQ_ID = REQUESTID;
ELSE
-- Get the request from third table (will return as blank if nothing found)
OPEN REQUEST FOR
SELECT REQ_TYPE, '-' AS REQ_TYPE_STATUS FROM THIRDTABLE
WHERE THIRDTABLE.REQ_ID = REQUESTID;
END IF;
END IF;