Return all possible combinations of values on colu

问题:

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

and turn this into all combinations:

1     2
1     4
1     5
2     4
2     5
4     5

回答1:

Assuming at least SQL 2005 for the CTE:

;with cteAllColumns as (
    select col1 as col
        from YourTable
    union
    select col2 as col
        from YourTable
)
select c1.col, c2.col 
    from cteAllColumns c1 
        cross join cteAllColumns c2 
    where c1.col < c2.col
    order by c1.col, c2.col

回答2:

You could cartesian join the table to itself, which would return all combinations of both columns.

select 
    distinct
    t1.Col1,
    t2.Col2
from 
    MyTable t1,
    MyTable t2

回答3:

You can do a self cross join...

SELECT a.Col1, b.Col2
FROM MyTable a
CROSS JOIN MyTable b

回答4:

I was looking for something that would do this using only the SQL available to Microsoft Access 2016. I ended up figuring out something that others may find useful. This code utilizes CROSS JOIN so I found that it is necessary to split the two columns into two separate tables (each with one column). The AND statement forces one column to be less than the other, thereby eliminating any repetitive 1-2, 2-1 sort of occurrences.

SELECT DISTINCT Table1.Column1, Table2.Column1
FROM Table1, Table2
WHERE Table1.Column1 <> Table2.Column1
AND Table2.Column1 < Table1.Column1;

回答5:

I think this has been overcomplicated!

Just:

SELECT distinct Col1, Col2

FROM MyTable

to get all possible combinations..

回答6:

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<t2_2.c
order by t2_1.c

回答7:

I find an inner join more intuitive because I use it more frequently than a cross join:

;with cteAllColumns as (
select col1 as col
    from YourTable
union
select col2 as col
    from YourTable
) 

select c1.col, c2.col 
from cteAllColumns c1 
    join cteAllColumns c2 on 1=1
where c1.col < c2.col
order by c1.col, c2.col

回答8:

Making Joe Answer easier

declare @t1 table  (col1 varchar(5))
insert @t1 
    select 'A' UNION
    select 'B' UNION
    select 'C' 


declare @t2 table  (col2 varchar(5))
insert @t2
    select '1' UNION
    select '2' UNION
    select '3' 


;with cteAllColumns as (
    select col1 as col
        from @t1
    union
    select col2 as col
        from @t2
)
select c1.col, c2.col 
    from cteAllColumns c1 
        cross join cteAllColumns c2 
    where c1.col < c2.col
    order by c1.col, c2.col

verify your combinations Qty (No of rows) http://www.calculatorsoup.com/calculators/discretemathematics/combinations.php