SELECT P.post_title, P.post_content, P.post_author,
  PM1.meta_value AS lat,
  PM2.meta_value AS lng
FROM wp_posts AS P
  LEFT JOIN wp_postmeta AS PM1 ON ( P.ID = PM1.post_id AND PM1.meta_key = 'ex_latitude' )
  LEFT JOIN wp_postmeta AS PM2 ON ( P.ID = PM2.post_id AND PM2.meta_key = 'ex_longitude' )
WHERE 1=1
  AND (
    PM1.meta_key = 'ex_latitude' OR
    PM2.meta_key = 'ex_longitude'
  )
  AND P.post_type = 'post'
  AND P.post_status = 'publish'
GROUP BY P.ID
ORDER BY P.ID DESC