Case always returns null?

Question

I have a subquery that gets the DATEDIFF of two dates. However the first case always returns null yet the actual sub query returns dates?!

CASE 
WHEN [date1] > [date2]
THEN DATEDIFF(DD,getdate(),date1) 
WHEN date1 < date2 
THEN DATEDIFF(DD,getdate(),date2) 
END[date diff]

FROM(

SELECT
licext.new_licenceId,
CASE 
WHEN CONVERT(time,licext.new_EmergencyLicenceExpiryDate) like '%23:00:00.000%'
THEN DATEADD(dd,1,CONVERT(date,licext.new_EmergencyLicenceExpiryDate))
ELSE CONVERT(date,licext.new_EmergencyLicenceExpiryDate)
END [date1], --EM Code

CASE 
WHEN CONVERT(time,licext.new_standardLicenceExpiryDate) like '%23:00:00.000%'
THEN DATEADD(dd,1,CONVERT(date,licext.new_standardLicenceExpiryDate))
ELSE CONVERT(date,licext.new_standardLicenceExpiryDate)
END [date2]  --FRL
from new_licenceExtensionBase licext
)QUERY

The reason the second cases are on there is because the database I am working with stores datetime in a really weird way, ie)If it has 23:00 at the end it actually means tomorrows date?! (This is a Microsoft CRM Database) -But that's a whole different matter.

EDIT:

It did have an ELSE clause which worked fine for date2 being bigger than date1, because that was being evaluated. For Example, the following code works fine for getting the difference between today and date2:

CASE 
WHEN [date1] > [date2]
THEN DATEDIFF(DD,getdate(),date1) 
ELSE DATEDIFF(DD,getdate(),date2) 
END[date diff]

EDIT 2:

I've just done a couple of tests: Using a select to return the dates works fine. -They return as expected.

Test 2: I've added a third WHEN to the query to say that when a date is null, return 1990-01-01..However it still returns null, Is my whole case being skipped over?

Answer 1

There's no ELSE in your first CASE, which means if none of your WHEN expressions are matched then it returns NULL.

My guess is there's an issue in your logic below that causes date1 and date2 to always be equal, which would miss both your WHENs in the first CASE and return NULL.