Question

I have a game table like:

CREATE TABLE game_piece(
  x Integer,
  y Integer,
  type Integer
);

Each (x,y) can only have 1 piece. Representing a grid (numbers being types):

1235
1134
9678

By connected I mean they have to be directly next to the origin in a vertical or horizontal fashion like:

 C   C=connected
COC  O=origin
 C

I’d like to check if there’s 3 pieces connected anywhere on the grid without needing to get the whole grid of the database and doing it in python, if there’s decent solution. Suggestions?

Answer 1

To clarify my comments on Xophmeister’s answer, like this:

SELECT o.x, o.y
FROM game_piece o
JOIN game_piece p
ON p.type = o.type
AND (
  (o.x = p.x AND p.y IN (o.y-1,o.y+1))
  OR
  (o.y = p.y AND p.x IN (o.x-1,o.x+1))
)
GROUP BY o.x, o.y
HAVING COUNT(*) > 1

And here it is working on your test data: http://sqlfiddle.com/#!3/0bd34/1

Edit: Since you only want to know if the condition exists, the best way to do it is to just shove LIMIT 1 on the end and see whether the query returns a result or not. For some reason sqlfiddle doesn’t like me putting the LIMIT in there, but I tested it on my server and it works just fine.