Creating a cross-tab in SQL Server

December 7, 2022

I have two equal sets (say, for instance, [1,2,3]) and want to create a table with all possible combinations so I can fill existing counts later in a new column instead of just counting and doing a GROUP BY.

What I have tried:

CREATE TABLE table1
(
    Var1 varchar(254),
    Var2 varchar(254)
)

INSERT INTO table1 (Var1) VALUES ('1')
INSERT INTO table1 (Var1) VALUES ('2')
INSERT INTO table1 (Var1) VALUES ('3')
INSERT INTO table1 (Var2) VALUES ('1')
INSERT INTO table1 (Var2) VALUES ('2')
INSERT INTO table1 (Var2) VALUES ('3')

This, however, results in:

Var1	Var2
1	NULL
2	NULL
3	NULL
NULL	1
NULL	2
NULL	3

When what I want is something like this:

Var1	Var2
1	1
1	2
1	3
2	1
2	2
2	3
3	1
3	2
3	3

How can I do this without having to insert each combination manually?

>Solution :

Using your example table and values:

select a.var1, b.Var2
  from table1 a, table1 b
  where a.var1 is not null and b.Var2 is not null
  order by a.var1, b.Var2

NOTE: you can do this with just a single column

CREATE TABLE table1(Var1 varchar(254))
INSERT INTO table1 (Var1) values ('1')
INSERT INTO table1 (Var1) values ('2')
INSERT INTO table1 (Var1) values ('3')

select a.var1, b.Var1 var2
  from table1 a, table1 b
  order by a.var1, b.Var1