Combining rows in SQL Server against all other rows - sql

Question

Say I have an table like this:
And I want to create a select which combines every non-null row against every other value such that I end up with:
etc, all the way up to 3 - 3 - 3
Can this be done in one select statement?

Answer 1

Since you want to combine values that are now on different rows, first you need to seperate them in subqueries (the with statements), then you can cross join these (cartesian product) to find all different combinations.
with
c1 as (select column1 from table where column1 is not null),
c2 as (select column2 from table where column2 is not null),
c3 as (select column3 from table where column3 is not null)
select *
from c1, c2, c3 -- no join condition returns all possible combinations

Answer 2

You can do it with two CROSS JOIN's:
DECLARE #tb AS TABLE
(
column1 INT
,column2 INT
,column3 INT
);
INSERT INTO #tb VALUES (1, NULL, NULL);
INSERT INTO #tb VALUES (2, NULL, NULL);
INSERT INTO #tb VALUES (3, NULL, NULL);
INSERT INTO #tb VALUES (NULL, 1, NULL);
INSERT INTO #tb VALUES (NULL, 2, NULL);
INSERT INTO #tb VALUES (NULL, 3, NULL);
INSERT INTO #tb VALUES (NULL, NULL, 1);
INSERT INTO #tb VALUES (NULL, NULL, 2);
INSERT INTO #tb VALUES (NULL, NULL, 3);
SELECT tb1.column1, tb2.column2, tb3.column3
FROM #tb tb1
CROSS JOIN #tb AS tb2
CROSS JOIN #tb AS tb3
WHERE tb1.column1 IS NOT NULL
AND tb2.column2 IS NOT NULL
AND tb3.column3 IS NOT NULL
ORDER BY tb1.column1, tb2.column2, tb3.column3;

Answer 3

Use cross join:
DECLARE #t table(col1 int, col2 int, col3 int)
INSERT #t values
(1, null, null),(2, null, null),(3, null, null),
(null, 1, null),(null, 2, null),(null, 3, null),
(null, null, 1),(null, null, 2),(null, null, 3)
SELECT t1.col1, t2.col2, t3.col3
FROM #t t1
CROSS JOIN #t t2
CROSS JOIN #t t3
WHERE t1.col1 is not null and t2.col2 is not null and t3.col3 is not null

Answer 4

You need to do a Cross Join here. Try this.
;WITH cte
AS (SELECT 1 cola,NULL colb, NULL colc
UNION
SELECT 2 cola,NULL colb,NULL colc
UNION
SELECT 3 cola,NULL colb,NULL colc
UNION
SELECT NULL cola,1 colb,NULL colc
UNION
SELECT NULL cola,2 colb,NULL colc
UNION
SELECT NULL cola,3 colb,NULL colc
UNION
SELECT NULL cola,NULL colb,1 colc
UNION
SELECT NULL cola,NULL colb,2 colc
UNION
SELECT NULL cola,NULL colb,3 colc)
SELECT *
FROM (SELECT a.cola
FROM cte a
WHERE cola IS NOT NULL) f
CROSS JOIN (SELECT b.colb
FROM cte b
WHERE colb IS NOT NULL) s
CROSS JOIN (SELECT c.colc
FROM cte c
WHERE colc IS NOT NULL) T