The SQL query from the article is
// Search the rows in the markers table
$query = sprintf("SELECT address, name, lat, lng, ( 3959 *
acos( cos( radians('%s') ) * cos( radians( lat ) ) *
cos( radians( lng ) - radians('%s') ) + sin( radians('%s') ) *
sin( radians( lat ) ) ) ) AS distance FROM markers HAVING distance <
'%s' ORDER BY distance LIMIT 0 , 20",
mysql_real_escape_string($center_lat),
mysql_real_escape_string($center_lng),
mysql_real_escape_string($center_lat),
mysql_real_escape_string($radius));
lat & lng are the fields to search in the database
$centre_lat and $centre_lng are parameters passed to the PHP file by
the function searchUrl in the calling function (centroid)
If you are not passing the centroid and radius your SQL should be
something like
$query = "SELECT address, name, lat, lng, ( 3959 *
acos( cos( radians(-37) ) * cos( radians( lat ) ) *
cos( radians( lng ) - radians(144) ) + sin( radians(-37') ) *
sin( radians( lat ) ) ) ) AS distance FROM markers HAVING distance < 5
ORDER BY distance LIMIT 0 , 20";
This will list all records from your database with a lat/lng within 5
miles of your centroid
Regards Davie
On Sep 29, 8:04 pm, Rossko <[email protected]> wrote:
> > SELECT *, ( 6371 * acos( cos( radians(-37) ) * cos( radians( -37.7833 ) ) *
> > cos( radians( 144.9833 ) - radians(144) ) + sin( radians(-37) ) * sin(
> > radians( -37.7833 ) ) ) ) AS distance FROM Geocode_AU HAVING distance < 5
> > ORDER BY distance
>
> It's wrong, you have all fixed numbers in your formula. Whatever the
> value of data in your table the formula will always evaluate to
> exactly the same value. If that is more than 5, no rows will ever be
> selected.
>
> As you want to SELECT some of your rows that fit your criteria (by
> radius) and discard other of your rows that don't fit your criteria,
> you need the formula to include or compare data from the rows it is
> examining.
>
> The example is
> SELECT id, ( 3959 * acos( cos( radians(37) ) * cos( radians( lat ) ) *
> cos( radians( lng ) ... etc
>
> where 37 is the "target" longitude for the centre of the search
> and 'lat' will substitute the value from the row of data to be tested,
> from each row in turn.
> etc
>
> > Also why I don't understand is why they rounded some of the lattitudes and
> > longitudes??? For example, they use -37 instead of the full -37.7833 and
> > 144 instead of
>
> As it says, "Here's the SQL statement that will find the closest 20
> locations that are within a radius of 25 miles to the 37, -122
> coordinate" They're not presenting an example SELECT within a radius
> of -37.7833, etc.
>
> > Seems odd that Google would post an example that doesn't work!???
>
> You could take it as a clue that your implementation, which isn't the
> same as Google's example, could be wrong?
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