Escaping Null Values From Quartile in SQl Server - sql-server

Question

I have create a table and inserted some records.
CREATE TABLE #t
(
ID INT IDENTITY(1,1) PRIMARY KEY,
val INT NULL
);
-- INSERT 10 values: 3 NULL, 7 integers
INSERT INTO #t SELECT NULL;
INSERT INTO #t SELECT NULL;
INSERT INTO #t SELECT NULL;
INSERT INTO #t SELECT 5;
INSERT INTO #t SELECT 7;
INSERT INTO #t SELECT 8;
INSERT INTO #t SELECT 9;
INSERT INTO #t SELECT 9;
INSERT INTO #t SELECT 11;
INSERT INTO #t SELECT 12;
Now when i am executing script to find quartile
SELECT *,
NTILE(4) OVER (ORDER BY val) As Q
FROM #t;
i am getting values as
ID val Q
---------
1 NULL 1
2 NULL 1
3 NULL 1
4 5 2
5 7 2
6 8 2
7 9 3
8 9 3
9 11 4
10 12 4
I don't want "Null" records and don't want to use "Where" clause.
I want result like this
ID val Q
---------
4 5 1
5 7 1
6 8 2
7 9 2
8 9 3
9 11 3
10 12 4

Answer 1

It strikes me that you might want NULL for the NTILE() value and to ignore the values for the calculation. You can get this by doing:
SELECT t.*,
(CASE WHEN val IS NOT NULL
THEN NTILE(4) OVER (PARTITION BY (CASE WHEN val IS NOT NULL THEN 'NOTNULL' ELSE 'NULL' END)
ORDER BY val
)
END) as Q
FROM #t t;
Or, perhaps more simply:
SELECT id, val, NTILE(4) OVER (ORDER BY val) As Q
FROM #t t
WHERE val IS NOT NULL
UNION ALL
SELECT id, val, NULL as q
FROM #t t
WHERE val IS NULL;

Answer 2

You could try this:
SELECT *,
CASE
WHEN val IS NULL THEN NULL
ELSE NTILE(4) OVER (
--Split NULL and NOT NULL into 2 different groups
PARTITION BY CASE WHEN val IS NULL THEN 0 ELSE 1 END
ORDER BY val)
END AS Q
FROM #t
You'll get:
ID val Q
1 NULL NULL
2 NULL NULL
3 NULL NULL
4 5 1
5 7 1
6 8 2
7 9 2
8 9 3
9 11 3
10 12 4