IS NULL being ignored - sql-server

Question

I am trying to run a query in T-SQL to pull back a data set based on a column being null.
This is a simplified version of the code:
SELECT
T1.Col1, T1.Col2,
T1.Col3, T1.Col4
FROM
table1 AS T1
INNER JOIN
table2 AS T2 ON T1.Col2 = T2.Col3
WHERE
T2.Col4 IS NULL
Problem is, the result includes rows where T2.Col4 are NULL and also not NULL, it's like the WHERE clause doesn't exist.
Any ideas would be greatly
UPDATE - full version of code:
SELECT
M.ref
,C.cname
,CL.clname
,C.ccity
,M.productLine
,M.code
,CL.date
,M.dept
,DPT.group
,TK2.tkname
,TK2.tkdept
FROM DB.dbo.manage AS M
OUTER JOIN DB.dbo.ClientManageRelationship AS CMR
ON CMR.RelatedEntityID = M.EntityID
OUTER JOIN DB.dbo.Client AS C
ON C.EntityID = CMR.EntityID
INNER JOIN DB.dbo.ManageCustomerRelationship AS MCR
ON MCR.EntityID = M.EntityID
INNER JOIN DB.dbo.Customer AS CL
ON CL.EntityID = MCR.RelatedID
INNER JOIN DB.dbo.timek AS TK
ON TK.tki = M.tkid
LEFT JOIN (SELECT Group = division, [Department] = newdesc, deptcode FROM DB.csrt.vw_rep_p_l_dept) AS DPT
ON tkdept = DPT.dept
LEFT JOIN (SELECT Name = TK2.tkfirst + ' ' + TK2.tklast, TK2.tki, TK2.dept, TK2.loc FROM DB.dbo.timek as TK2 WITH(NOLOCK)) AS TK2
ON TK2.tki = M.tkid
WHERE DPT.Department = 'Casualty'
AND UPPER (C.ClientName) LIKE '%LIMITED%'
AND CL.date > '31/12/2014'
AND CL.Date IS NULL
AND TK.tkloc = 'loc1' OR TK.tkloc = 'loc2'
ORDER BY M.ref

Answer 1

My first answer would be because you're using INNER JOIN. This only returns matches between the 2 tables. TRY FULL OUTER JOIN which will return all values regardless of matches and will include NULLS.
If you were looking to return all rows regardless of matches including NULLS from only one of the tables then use RIGHT or LEFT JOIN.
Say i had 2 tables ('Person' and 'Figure'). Not every person may have entered a figure on any one day. But an example may be i want to return all people regardless of whether they entered a figure or not on a certain day.
My initial approach to this would be a LEFT join because i want to return of all the people(left table) regardless of there being any matches in the figure table(right table)
FROM Person P
LEFT JOIN Figure F
ON P.ID = F.ID
This would produce a result such as
Name Figure
Sam 20
Ben 30
Matt NULL
Simon NULL
Whereas,
An inner join would produce only matching values not including nulls
Name Figure
Sam 20
Ben 30
Left join works the same way as right join but in the opposite direction. This is most likely the problem you were facing. But i hope this helped

Answer 2

I think the problem is in the last part of the where condition.
You should use brackets.
`WHERE DPT.Department = 'Casualty'
AND UPPER (C.ClientName) LIKE '%LIMITED%'
AND CL.date > '31/12/2014'
AND CL.Date IS NULL
AND (TK.tkloc = 'loc1' OR TK.tkloc = 'loc2')`
or
`WHERE DPT.Department = 'Casualty'
AND UPPER (C.ClientName) LIKE '%LIMITED%'
AND CL.date > '31/12/2014'
AND CL.Date IS NULL
AND TK.tkloc IN ('loc1', 'loc2')`