Return all possible combinations of values on columns in SQL

Question

How do I return a list of all combinations of values in 2 columns so they are new rows in T-SQL?

e.g.

Col1, Col2
----  ----
1     2
1     4
1     5
<         


        

Answer 1

This uses 2 cte's, the first simply reproduces your input table, the second turns both columns into a single column. The final select crossjoin's this set to itself to produce the required output

with t(c1,c2)
AS
(
    select 1,2
    union select 1,4
    union select 1,5
)
,t2(c)
as
(
    select c1 from t
    union select c2 from t
)
select t2_1.c, t2_2.c
from t2 t2_1 
cross join t2 t2_2
where t2_1.c