Mysql Order By Problematic - mysql

Question

Okay, I'm having some difficulties with order by. Here is the problem I need to solve:
In the database I have written every tile of a map, that is 101 x 101 big. The table has 3 columns(ID, x, y), now I gotta select all the tiles in some radious. For example, I used this query:
SELECT *
FROM tile
WHERE ((x >= -3 AND x <= 3)
AND (y >= -3 AND y <= 3))
ORDER BY x ASC, y DESC;
This query selects all tiles in radius of 3 of the given coordinate (0|0) for now.
But, it doesn't sort them the way I want it to. Basically, the output must be like this.
But this is the closest I got.
http://prntscr.com/zqjd7
Edit:
Disregard the double values, had double inputs for each coordinate. Haven't seen it.

Answer 1

It seems that your problem is around the ASC / DESC modificator.
But since we're here, wouldn't you prefer to use a distance formula? Something near
SELECT x, y FROM tile WHERE
(
POW(x-#var1, 2) + POW(y-#var2, 2) <= POW(3, 2)
)
ORDER BY x DESC, y ASC;
Here, given a point P (m,n), we shall know the distance to a fixed point Q (x,y) by acerting D(P,Q) = SQRT( (x-m)² + (y-n)² ). As much as it has to be less than (or equals) your desired radius (= 3), we have so SQRT( (x-m)² + (y-n)² ) <= 3, or better, (x-m)² + (y-n)² <= 3², raising both terms to its square power.
SQL-language speaking, we write POW(x-m, 2) + POW(y-n, 2) <= POW(3, 2), willing to say that the distance between (x,y) and (m,n) is last than or equal 3.
About #var, it's where you enter your input value. More specifically, they are session variables, but you don't really want to use it to perform a select; just substitute them by any number you want, e.g. you can choose the origin (0,0) by putting 0 on place of #var1 and #var2.
[Update]
Well... It's always a good idea to test your code before answering. In fact I should have suggested to order firstly by y, since we first care about ordering rows to display on screen. The following code was (finally) tested (on test DB); my last suggest is to create the following index (index_y_x):
USE `test` ;
CREATE TABLE IF NOT EXISTS `test`.`tile` (
`id` INT(11) UNSIGNED NOT NULL AUTO_INCREMENT ,
`x` INT(11) NULL DEFAULT 0 ,
`y` INT(11) NULL DEFAULT 0 ,
PRIMARY KEY (`id`) ,
INDEX `index_y_x` (`y` DESC, `x` ASC) )
ENGINE = InnoDB
DEFAULT CHARACTER SET = utf8;
INSERT tile (x,y) VALUES
(-2,-2),(-2, -1),(-2, 0),(-2, 1),(-2, 2),
(-1,-2),(-1, -1),(-1, 0),(-1, 1),(-1, 2),
(0,-2), (0, -1), (0, 0), (0, 1), (0, 2),
(1,-2), (1, -1), (1, 0), (1, 1), (1, 2),
(2,-2), (2, -1), (2, 0), (2, 1), (2, 2);
SELECT x, y FROM tile
WHERE POW(x-3, 2) + POW(y-3, 2) <= POW(3, 2)
ORDER BY y DESC, x ASC;
This returns items near the point (3,3), in a range of 3 units