Question

Refresh my memory. I can’t recall how to join tuples (a,b) and (c) to produce (a,b)*(c). For example:

n
---
0
1
2

And

site_id     value
----------- -------------
1           a
1           b
2           c

I’d like to end up with:

site_id     value          n
----------- -------------- -- 
1           a              0
1           a              1
1           a              2 
1           b              0
1           b              1
1           b              2
2           c              0
2           c              1
2           c              2

How can I achieve this?

Answer 1

That’s called a CROSS JOIN, also known as the Cartesian product.

SELECT *
FROM Table1
CROSS JOIN Table2

You can also do it without the JOIN keyword just by using a comma:

SELECT * FROM Table1, Table2

Here’s full test code you can use to verify that it works:

CREATE TABLE Table1 (n int NOT NULL);
INSERT INTO Table1 (n) VALUES
(0),
(1),
(2);

CREATE TABLE Table2 (site_id int NOT NULL, value nvarchar(100) NOT NULL);
INSERT INTO Table2 (site_id, value) VALUES
(1, 'a'),
(1, 'b'),
(2, 'c');

SELECT Table2.site_id, Table2.value, Table1.n FROM Table1, Table2

Results:

site_id  value  n
      1      a  0
      1      a  1
      1      a  2
      1      b  0
      1      b  1
      1      b  2
      2      c  0
      2      c  1
      2      c  2