DB cartesian product on same table
Asked Answered
E

2

8

I have a one column table with three rows as below:

col1

team1
team2
team3
team4

I want to do a self cartesian join with result as below:
team1, team2
team1, team3
team1, team4
team2, team3
team2, team4
team3, team4

Evan answered 7/8, 2015 at 9:16 Comment(0)
U
7

cartesian product is cross join in DB terms, you can remove rows where teams are equal in where clause:

select
    t1.col1, t2.col1
from teams as t1
    cross join teams as t2
where
    t1.col1 <> t2.col1
Unlucky answered 7/8, 2015 at 9:49 Comment(1)
Small correction: To get the desired result specified in the question (combination rather than permutation), you need where t1.col1 > t2.col1. Otherwise you wouldn't get (1,1), but you'd still get both (1,2) and (2,1) when you just want HALF of the Cartesian product for all combinations.Pluckless
S
1

You can join both tables together for the intended output like this:

select t1.col1, t2.col1
from table t1
join table t2
on t1.col1 <> t2.col1
Stomachic answered 7/8, 2015 at 9:29 Comment(0)

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