SQL Connect By Level sometimes works, sometimes doesn't can't understand why - sql

Question

I am trying to run the query in Oracle, and if I change the round to 0, I get a result, but anytime there are decimals I am not getting a result back when using the connect by level part. But if I run I my query from after n.n= I get the result.
Reason I am trying to use the connect by level is I have a requirement to put my entire query into the where clause as in the application there is a restriction to do the group by clause I need.
SELECT n.n
FROM
(SELECT TO_NUMBER( LEVEL) - 1 n FROM DUAL CONNECT BY LEVEL <= 1000 ) n
WHERE n.n =
(subquery)
Examples of values I have which work in HOURS seem to be like whole number, wo when these are summed they are still whole numbers
5
10
5
5
20
But where I have seen the query not work is where I have decimal values such as:
3.68
2.45
5
10
5
Table:ASSIGNMENTS_M
Table: RESULT_VALUES
Columns: Result_ID, Assignment_ID, Date_Earned, Hours
INSERT INTO RESULT_VALUES(Result_ID, Assignment_ID, Date_Earned, Hours) VALUES(50,123456,to_date('01/02/2020', 'DD/MM/YYYY'),3.68 51,230034,to_date('02/02/2020', 'DD/MM/YYYY'),5 52,123456,to_date('03/02/2020', 'DD/MM/YYYY'),10 53,123456,to_date('04/02/2020', 'DD/MM/YYYY'),5 60,123456,to_date('05/02/2020', 'DD/MM/YYYY'),5 90,123456,to_date('06/02/2020', 'DD/MM/YYYY'),5 2384,123456,to_date('07/02/2020', 'DD/MM/YYYY'),10);
Expected Result = 38.68

Answer 1

Here's one solution, even though it's odd you want to do this:
The adjusted fiddle:
Working test case
This increments by 0.1 to find the matching row:
SELECT n.n
FROM ( SELECT TO_NUMBER(LEVEL)/10 - 1 n FROM DUAL CONNECT BY LEVEL <= 1000 ) n
WHERE n.n = (
SELECT round((sum(P2.HOURS)),1) FTE
FROM ASSIGNMENTS_M P1, RESULT_HOURS P2
WHERE P2.date_earned BETWEEN to_date('2020/01/01','YYYY/MM/DD') AND to_date('2020/10/31','YYYY/MM/DD')
AND P1.ASSIGNMENT_ID = 123456
GROUP BY P1.ASSIGNMENT_ID
)
;
This increments by 1 to find the matching row, but adjusts the calculation to allow this:
SELECT n.n / 10
FROM ( SELECT TO_NUMBER(LEVEL) - 1 n FROM DUAL CONNECT BY LEVEL <= 1000 ) n
WHERE n.n = (
SELECT round((sum(P2.HOURS)),1) FTE
FROM ASSIGNMENTS_M P1, RESULT_HOURS P2
WHERE P2.date_earned BETWEEN to_date('2020/01/01','YYYY/MM/DD') AND to_date('2020/10/31','YYYY/MM/DD')
AND P1.ASSIGNMENT_ID = 123456
GROUP BY P1.ASSIGNMENT_ID
) * 10
;
The result:
None of your results match the number sequence generated by the n derived table:
SELECT p1.assignment_id, round((sum(P2.HOURS)),1) FTE
FROM ASSIGNMENTS_M P1, RESULT_HOURS P2
WHERE P2.date_earned BETWEEN to_date('2020/01/01','YYYY/MM/DD') AND to_date('2020/10/31','YYYY/MM/DD')
AND P1.ASSIGNMENT_ID = 123456
GROUP BY P1.ASSIGNMENT_ID
;
Result:
+---------------=+
| id | fte |
+----------------+
| 123456 | 43.7 |
+----------------+
That's the reason. Now how do you want to change this logic?
Do you want an approximate comparison or do you want your sequence to be in 0.1 increments?