Warning: Null value is eliminated by an aggregate or other SET operation in Aqua Data Studio
I have a problem when data is null and the warning has appear when the result is display. How to solve this problem?. How to change the null data to 0 when no data in the table?.
This is my code:-
SELECT DISTINCT c.username AS assigner_officer,
d.description AS ticketcategory,
(SELECT Count(closed)
FROM ticket
WHERE assigned_to = c.user_id
AND closed IS NOT NULL
GROUP BY assigned_to)closedcases,
(SELECT Count(closed)
FROM ticket
WHERE assigned_to = c.user_id
AND closed IS NULL
GROUP BY assigned_to)opencases
FROM ticket a
JOIN ticketlog b
ON a.ticketid = b.ticketid
JOIN access c
ON a.assigned_to = c.user_id
JOIN ticket_category d
ON a.cat_code = d.id
JOIN lookup_department e
ON a.department_code = e.code
The result appear like this:-
Warnings: --->
W (1): Warning: Null value is eliminated by an aggregate or other SET operation.
<---
assigner_officer ticketcategory closedcases opencases
------------------- ----------------- -------------- ------------
abdulhafiz Enquiry (null) 0
affan Enquiry 12 (null)
amirul Enquiry 1 (null)
azrul_fahmi Enquiry 45 0
Azwani Enquiry (null) 0
chai Enquiry 4 (null)
dalinawati Enquiry 1 0
Emmy Complaints (null) 0
Fadhlia Enquiry 38 0
fairulhalif Others 1 (null)
farikh Enquiry (null) 0
ismailh Enquiry 28 0
izzahanna Enquiry (null) 0
Kamsuzilawati Enquiry 1 (null)
You would mostly be using COUNT
to summarize over a UID. Therefore
COUNT([uid])
will produce the warning:
Warning: Null value is eliminated by an aggregate or other SET operation.
whilst being used with a left join, where the counted object does not exist.
Using COUNT(*)
in this case would also render incorrect results, as you would then be counting the total number of results (ie parents) that exist.
Using COUNT([uid])
IS a valid way of counting, and the warning is nothing more than a warning. However if you are concerned, and you want to get a true count of uids in this case then you could use:
SUM(CASE WHEN [uid] IS NULL THEN 0 ELSE 1 END) AS [new_count]
This would not add a lot of overheads to your query. (tested mssql 2008)
One way to solve this problem is by turning the warnings off.
SET ANSI_WARNINGS OFF;
GO
Use ISNULL(field, 0)
It can also be used with aggregates:
ISNULL(count(field), 0)
However, you might consider changing count(field) to count(*)
Edit:
try:
closedcases = ISNULL(
(select count(closed) from ticket
where assigned_to = c.user_id and closed is not null
group by assigned_to), 0),
opencases = ISNULL(
(select count(closed) from ticket
where assigned_to = c.user_id and closed is null
group by assigned_to), 0),
You want to put the ISNULL
inside of the COUNT
function, not outside:
Not GOOD: ISNULL(COUNT(field), 0)
GOOD: COUNT(ISNULL(field, 0))