Condense or merge rows with null values not using group by - sql

Question

Let's say I have a select which returns the following Data:
select nr, name, val_1, val_2, val_3
from table
Nr. | Name | Value 1 | Value 2 | Value 3
-----+------------+---------+---------+---------
1 | Max | 123 | NULL | NULL
1 | Max | NULL | 456 | NULL
1 | Max | NULL | NULL | 789
9 | Lisa | 1 | NULL | NULL
9 | Lisa | 3 | NULL | NULL
9 | Lisa | NULL | NULL | Hello
9 | Lisa | 9 | NULL | NULL
I'd like to condense the rows down to the bare minimum with.
I want the following result:
Nr. | Name | Value 1 | Value 2 | Value 3
-----+------------+---------+---------+---------
1 | Max | 123 | 456 | 789
9 | Lisa | 1 | NULL | Hello
9 | Lisa | 3 | NULL | NULL
9 | Lisa | 9 | NULL | NULL
For condensing the rows with Max (Nr. 1) a group by of the max values would help.
select nr, name, max(val_1), max(val_2), max(val_3)
from table
group by nr, name
But I am unsure how to get the desired results for Lisa (Nr. 9). The row for Lisa contains a value in the Value 3 column, in this example it's condensed with the first row that matches Nr and Name and has a Null value in Value 3.
I'm thankful for every input!

Answer 1

Basic principle is same as Vladimir's solution. This uses UNPIVOT and PIVOT
with cte as
(
select nr, name, col, val,
rn = row_number() over(partition by nr, name, col order by val)
from [table]
unpivot
(
val
for col in (val_1, val_2, val_3)
) u
)
select *
from (
select nr, name, rn, col, val
from cte
) d
pivot
(
max (val)
for col in ([val_1], [val_2], [val_3])
) p

Answer 2

Here is one way to do it. Assign a unique row number for each column by sorting them in such a way that NULLs come last and then join them back together using these row numbers and remove rows with all NULLs.
Run just the CTE first and examine the intermediate result to understand how it works.
Sample data
DECLARE #T TABLE (Nr varchar(10), Name varchar(10), V1 varchar(10), V2 varchar(10), V3 varchar(10));
INSERT INTO #T VALUES
('1', 'Max ', '123' , NULL , NULL ),
('1', 'Max ', NULL , '456', NULL ),
('1', 'Max ', NULL , NULL , '789'),
('9', 'Lisa', '1' , NULL , NULL ),
('9', 'Lisa', '3' , NULL , NULL ),
('9', 'Lisa', NULL , NULL , 'Hello'),
('9', 'Lisa', '9' , NULL , NULL );
Query
WITH CTE
AS
(
SELECT
Nr
,Name
,V1
,V2
,V3
-- here we use CASE WHEN V1 IS NULL THEN 1 ELSE 0 END to put NULLs last
,ROW_NUMBER() OVER (PARTITION BY Nr ORDER BY CASE WHEN V1 IS NULL THEN 1 ELSE 0 END, V1) AS rn1
,ROW_NUMBER() OVER (PARTITION BY Nr ORDER BY CASE WHEN V2 IS NULL THEN 1 ELSE 0 END, V2) AS rn2
,ROW_NUMBER() OVER (PARTITION BY Nr ORDER BY CASE WHEN V3 IS NULL THEN 1 ELSE 0 END, V3) AS rn3
FROM #T AS T
)
SELECT
T1.Nr
,T1.Name
,T1.V1
,T2.V2
,T3.V3
FROM
CTE AS T1
INNER JOIN CTE AS T2 ON T2.Nr = T1.Nr AND T2.rn2 = T1.rn1
INNER JOIN CTE AS T3 ON T3.Nr = T1.Nr AND T3.rn3 = T1.rn1
WHERE
T1.V1 IS NOT NULL
OR T2.V2 IS NOT NULL
OR T3.V3 IS NOT NULL
ORDER BY
T1.Nr, T1.rn1
;
Result
+----+------+-----+------+-------+
| Nr | Name | V1 | V2 | V3 |
+----+------+-----+------+-------+
| 1 | Max | 123 | 456 | 789 |
| 9 | Lisa | 1 | NULL | Hello |
| 9 | Lisa | 3 | NULL | NULL |
| 9 | Lisa | 9 | NULL | NULL |
+----+------+-----+------+-------+