Using LIMIT

[dcace]

If I'm querying a table where I know it's going to be a unique answer should I put LIMIT 0,1 . My thinking being that if the record I'm looking for is the 3rd of 250,000 then using LIMIT will stop the query after it's found the record instead of going through the other 249,997 records. Is this right?

$sql = "SELECT * FROM db_sector WHERE sector_x = '" . $x . "' AND sector_y = '" . $y . "' LIMIT 0,1";
$result = mysql_query($sql);
$sector_id = mysql_result($result, "0", "db_sector.sector_id");

[laserlight]

Yes, but you can simplify to just LIMIT 1

[NogDog]

If it is sure to be unique and if you have an index on the column you're using in the where clause, then I doubt there would be any meaningful time savings.

I don't know if the limit is applied after it finds all matching rows, or if it's smart enough to know that since there's no order by clause it can just stop as soon as it finds a match. You could always try some timing tests and gather some empirical data. Who, knows, perhaps the overhead of adding the LIMIT clause will actually add some time?