Re: Understanding behavior of SELECT with multiple unnested columns

Basically you are getting Cartesian joins on the row output of
unnest()

Well that's what I expected too.  Except look at this example, after you delete c:

testdb=# DELETE FROM t2 where val='c';

DELETE 1

testdb=# SELECT * from t1, t2;

 val | val

-----+-----

   1 | a

   1 | b

   2 | a

   2 | b

(4 rows)

 

And compare to:

SELECT unnest(array[1,2]),unnest(array['a','b']);

 unnest | unnest 

--------+--------

      1 | a

      2 | b

(2 rows)

You can see they are not the same!