Calculating spatial distances in mysql and order by distance

Question

I have 3 tables with the following fields:

1. org (org_id, org_name, location)
2. office (office_id, office_name, location, org_id)
3. project (project_id, project_name, location)

I want to find the closest offices to a given project

SELECT office.office_name, org.org_name, 
       st_distance_sphere(office.location, project.location)*0.001 as 
       distance 
FROM   office JOIN org JOIN project
WHERE  office.org_id=org.org_id AND 
       project.project_id=7 
ORDER BY distance asc;

The above query works and gives me closest offices to a project, but I need to get only 1 closest office per org

Hence I tried, the following using semi-join

SELECT office.office_name, org.org_name, 
       st_distance_sphere(office.location, project.location)*0.001 as  
       distance 
FROM  office JOIN org JOIN project  
INNER JOIN 
  ( SELECT org.org_id as orgid1, 
       min(st_distance_sphere(office.location, project.location)*0.0001) as 
       distance1 
   FROM office JOIN org JOIN project 
   WHERE 
      office.org_id=org.org_id and project.project_id=7
   GROUP BY org.org_id
   ) AS t 
     ON t.orgid1=org.org_id and t.distance1=min(st_distance_sphere(office.location,project.location)*0.001) 
 WHERE  office.org_id=org.org_id AND project.project_id=7 ;

Using this, I get the following error and the reason seems to be the min(st_distance_sphere) function. Removing that removes the error, but i don't get the desired results.

ERROR 1111 (HY000): Invalid use of group function

What am i doing wrong ? Any thoughts highly appreciated. Thanks

Answer 1

I need to get only 1 closest office per org

SELECT 
  A.office_name, A.org_name, A.distance
FROM
  (SELECT 
    office.office_name,
    org.org_name, 
    st_distance_sphere(office.location, project.location)*0.001 as distance 
  FROM  office JOIN org JOIN project
  WHERE  office.org_id=org.org_id AND 
       project.project_id=7) A 
  JOIN 
  (SELECT 
     org.org_name, 
     MIN(st_distance_sphere(office.location, project.location)*0.001) as distance 
  FROM   office JOIN org JOIN project
  WHERE  office.org_id=org.org_id AND 
       project.project_id=7
  GROUP BY org.org_name) B
  ON A.org_name=B.org_name AND A.distance=B.distance
ORDER BY A.distance ASC;