Where Not

Question

These both not returning same number, am i missing anything, I would like change the first query to write in other format, because i have lot of and conditions like this. I have given only one as example.
-- Original query ; working
SELECT COUNT(*) FROM P
INNER JOIN R WITH ( NOLOCK )
ON R.Id = P.Id
where P.Pk NOT IN (
SELECT p.Pk
WHERE R.Name = 'S'
AND p.Type = 'O' )
and R.Date = '7/16/2014'
-- Test query ; not returning same rows as above
SELECT COUNT(*) FROM P
INNER JOIN R WITH ( NOLOCK ) ON R.Id = P.Id
where NOT (R.Name = 'S' AND p.Type = 'O')
and R.Date = '7/16/2014'

Answer 1

Those two statements will not return the same result if either R.Name or P.Type is NULL and R.Date = '7/16/2014'
To see why that is true, consider the case where R.Name is NULL and P.Type = 'O'.
The first query's inner select is Select p.Pk WHERE R.Name = 'S' AND p.Type = 'O'.  That will return zero rows because R.Name is NULL.  So the NOT IN will be TRUE and since the R.Date condition is TRUE so the entire where is true and that row is
counted.
In the second case, you check if R.Name = 'S'.  Since R.Name is NULL, the result of that logical comparison is UNKNOWN (that is, neither true nor false).  You then AND that with p.Type = 'O' which is TRUE.  So you get UNKNOWN AND TRUE - the
result of that is UNKNOWN.  You then do a NOT of that UNKNOWN values which is still UNKNOWN.  You then and that with R.Date = '7/16/2014', so the final result of your where condition is UNKNOWN.  So this row is not counted.
So the first and second queries can return different results.
I gather from your question that you want a query using the form of the second query that will return the same result as the first query.  To do that you have to handle the NULL's.  One way would be to do
SELECT COUNT(*) FROM P
INNER JOIN R ON R.Id = P.Id
where Not (IsNull(R.Name, 'S') <> 'S' And IsNull(p.Type, 'O') <> 'O')
and R.Date = '7/16/2014'
Tom