Q:

mysql update table from another table

I'm trying to update a field in one table, from the sum of another field, in another table.
company_tbl (PRIMARY, companySize, companyName)
location_tbl (PRIMARY, companyID, locationSize, locationName)
The two tables link by company_tbl.PRIMARY = location_tbl.companyID
update company_tbl comp, location_tbl loc
set companySize = sum(locationSize)
where comp.PRIMARY = loc.companyID

I'm getting an error of 'invalid use of group function'
A company can have multiple locations
Is what I want to do possible?  I want to take the sum of locations, that belong to a specific company, and update the companySize with the sum.
Thanks!

A:

Use:
UPDATE company_tbl comp
   SET companySize = (SELECT SUM(lt.locationSize)
                        FROM location_tbl lt
                       WHERE lt.companyid = comp.primary)

...or you could use a view, containing:
   SELECT c.primary,
          COALESCE(SUM(lt.locationsize), 0) AS companysize
     FROM company_tbl c
LEFT JOIN location_tbl lt ON lt.companyid = c.primary

