counting rows via php is faster than COUNT in SQL? - php

Question

In short my question is this: Why is this
SELECT r.x, r.y FROM `base` AS r
WHERE r.l=50 AND AND r.n<>'name' AND 6=(SELECT COUNT(*) FROM surround AS d
WHERE d.x >= r.x -1 AND d.x <= r.x +1 AND
d.y>=r.y -1 AND d.y<=r.y +1 AND d.n='name')
a lot slower than this:
$q="SELECT x,y FROM `base` WHERE l=50 AND n<>'name'";
$sr=mysql_query($q);
if(mysql_num_rows($sr)>=1){
while($row=mysql_fetch_assoc($sr)){
$q2="SELECT x,y FROM surround WHERE n='name' AND x<=".
($row["x"]+1)." AND x>=".($row["x"]-1).
" AND y<=".($row["y"]+1)." AND y>=".($row["y"]-1)." ";
$sr2=mysql_query($q2);
if(mysql_num_rows($sr2)=6){
echo $row['x'].','.$row[y].'\n';
}
}
}
The php version takes about 300 ms to complete, if I run the "pure SQL" version, be it via phpadmin or via php, that takes roughly 5 seconds (and even 13 seconds when I used BETWEEN for those ranges of x and y)
I would suspect that the SQL version would in general be faster, and more efficient at least, so I wonder, am I doing something wrong, or does it make sense?
EDIT: I added the structure of both tables, as requested:
CREATE TABLE IF NOT EXISTS `base` (
`bid` int(12) NOT NULL COMMENT 'Base ID',
`n` varchar(25) NOT NULL COMMENT 'Name',
`l` int(3) NOT NULL,
`x` int(3) NOT NULL,
`y` int(3) NOT NULL,
`LastModified` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
UNIQUE KEY `coord` (`x`,`y`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
CREATE TABLE IF NOT EXISTS `surround` (
`bid` int(12) NOT NULL COMMENT 'Base ID',
`n` varchar(25) NOT NULL COMMENT 'Name',
`l` int(3) NOT NULL,
`x` int(3) NOT NULL,
`y` int(3) NOT NULL,
`LastModified` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
UNIQUE KEY `coord` (`x`,`y`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
EDIT 2:
EXPLAIN SELECT for the query above: (the key coord is the combination of x and y)
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY r range coord,n coord 4 NULL 4998 Using where
2 DEPENDENT SUBQUERY d ALL coord NULL NULL NULL 57241 Range checked for each record (index map: 0x1)

Answer 1

You are joinning two tables by yourself. you're an optimizer. you choice 'base' table is outer table for nested loop join. I guess MySQL's optimizer produced execution plan and it was not same as you.
so people want EXPLAIN output to see join order and to check index was used.
by the way, can you try this query?:
SELECT r.x, r.y
FROM `base` AS r, surround AS d
WHERE r.l=50
AND r.n<>'name'
AND d.x >= r.x -1
AND d.x <= r.x +1
AND d.y>=r.y -1
AND d.y<=r.y +1
AND d.n='name'
GROUP BY r.x, r.y
HAVING COUNT(*) = 6
UPDATED
how your original query works
It was first time seeing Range checked for each record (index map: 0x1) so I can't figure out how your query works. MySQL Manual gives us some information about it. It seems like that every row in surround (surround has 57k rows?) is compare to base's x,y. If so, your query is evaluated using 3 depth nested loop join. (base => surround => base) and moreover every row in surround is compared (this is inefficient)
I will make more effort to find how it works later. It's time to work.