max distance from center - general

SQL

use dewiki_p;
set @iso1:='DE';
#set @iso2:='' or code
set @iso2:='RP';

select distinct gt_country, gt_region from geo_tags order by 1,2 asc limit 10;

select sqrt((gt_lat - cen_gt_lat)*(gt_lat - cen_gt_lat) + (gt_lon - cen_gt_lon)*(gt_lon - cen_gt_lon)) as distanzungefaehr, 
       gt_lat, gt_lon, gt_page_id, gt_name,
       (select page_title from page where page_id = gt_page_id) as title,
       (select distinct gt_country, gt_region from geo_tags order by 1,2) as iso1, iso2,
       gt_country,gt_region from geo_tags,
       (select avg(gt_lat) cen_gt_lat,avg(gt_lon) cen_gt_lon,count(*) from geo_tags
        where 
        	case 
        		when @iso2=''
        		then gt_country=@iso1 and gt_region is null
        		else gt_country=@iso1 and gt_region=@iso2
        		end) as zentrumdavon
        where
        	case
            	when @iso2=''
                then gt_country=@iso1 and gt_region is null
                else gt_country=@iso1 and gt_region=@iso2
                end
       order by 1 desc limit 50;
SQL

Checking query status...
