Changing a SUM returned NULL to zero - sql

Question

I have a stored procedure as follows:
CREATE PROC [dbo].[Incidents]
(#SiteName varchar(200))
AS
SELECT
(
SELECT SUM(i.Logged)
FROM tbl_Sites s
INNER JOIN tbl_Incidents i
ON s.Location = i.Location
WHERE s.Sites = #SiteName AND i.[month] = DATEADD(mm, DATEDIFF(mm, 0, GetDate()) -1,0)
GROUP BY s.Sites
) AS LoggedIncidents
'tbl_Sites contains a list of reported on sites.
'tbl_Incidents contains a generated list of total incidents by site/date (monthly)
'If a site doesn't have any incidents that month it wont be listed.
The problem I'm having is that a site doesn't have any Incidents this month and as such i got a NULL value returned for that site when i run this proc, but i need to have a zero/0 returned to be used within a chart in SSRS.
I've tried using coalesce and isnull to no avail.
SELECT COALESCE(SUM(c.Logged,0))
SELECT SUM(ISNULL(c.Logged,0))
Is there a way to get this formatted correctly?
Cheers,
Lee

Answer 1

Put it outside:
SELECT COALESCE(
(
SELECT SUM(i.Logged)
FROM tbl_Sites s
INNER JOIN tbl_Incidents i
ON s.Location = i.Location
WHERE s.Sites = #SiteName AND i.[month] = DATEADD(mm, DATEDIFF(mm, 0, GetDate()) -1,0)
GROUP BY s.Sites
), 0) AS LoggedIncidents
If you are returning multiple rows, change INNER JOIN to LEFT JOIN
SELECT COALESCE(SUM(i.Logged),0)
FROM tbl_Sites s
LEFT JOIN tbl_Incidents i
ON s.Location = i.Location
WHERE s.Sites = #SiteName AND i.[month] = DATEADD(mm, DATEDIFF(mm, 0, GetDate()) -1,0)
GROUP BY s.Sites
By the way, don't put any function or expression inside aggregate functions if it's not warranted, e.g. don't put ISNULL, COALESCE inside of SUM, using function/expression inside aggregation cripples performance, the query will be executed with table scan

Answer 2

You'll have to use ISNULL like this -
ISNULL(SUM(c.Logged), 0)
Or, as Michael said, you can use a Left Outer Join.

Answer 3

I encountered this problem in Oracle.
Oracle does not have an ISNULL() function. However, we can use the NVL() function to achieve the same result:
NVL(SUM(c.Logged), 0)

Answer 4

The easiest, and most readable, way I've found to accomplish this is through:
CREATE PROC [dbo].[Incidents]
(#SiteName varchar(200))
AS
SELECT SUM(COALESCE(i.Logged, 0)) AS LoggedIncidents
FROM tbl_Sites s
INNER JOIN tbl_Incidents i
ON s.Location = i.Location
WHERE s.Sites = #SiteName
AND i.[month] = DATEADD(mm, DATEDIFF(mm, 0, GetDate()) -1,0)
GROUP BY s.Sites

Answer 5

You could wrap the SELECT in another SELECT like so:
CREATE PROC [dbo].[Incidents]
(#SiteName varchar(200))
AS
SELECT COALESCE(TotalIncidents ,0)
FROM (
SELECT
(
SELECT SUM(i.Logged) as TotalIncidents
FROM tbl_Sites s
INNER JOIN tbl_Incidents i
ON s.Location = i.Location
WHERE s.Sites = #SiteName AND i.[month] = DATEADD(mm, DATEDIFF(mm, 0, GetDate()) -1,0)
GROUP BY s.Sites
) AS LoggedIncidents
)

Answer 6

Just ran into this problem, Kirtan's solution worked for me well, but the syntax was a little off. I did like this:
ISNULL(SUM(c.Logged), 0)
Post helped me solve my problem though so thanks to all.

Answer 7

The code you've posted above
SELECT SUM(ISNULL(c.Logged,0))
would not work due to wrong order
what would work is the following
SELECT ISNULL(SUM(c.Logged),0)
It evaulates the expression SUM then if it returns NULL it is replaced with 0.