SELECT c.timestamp, c.wert, count( a.wert ) , avg( a.wert )
FROM Counter.`99999910` AS c
LEFT JOIN alt.`statusanz` AS a ON a.Zeitstempel
BETWEEN c.timestamp - 0.005
AND c.timestamp + 0.005
WHERE UNIX_TIMESTAMP( c.timestamp )
BETWEEN 1295859173
AND 1295869173
GROUP BY c.timestamp
LIMIT 0 , 30

SELECT     c.timestamp, c.wert, UNIX_TIMESTAMP(c.timestamp) AS unix_time, a.wert
  FROM (SELECT c.timestamp AS stamp1, max(a.Zeitstempel) AS stamp2
          FROM Counter.`99999910` as c
               LEFT JOIN alt.`statusanz` AS a ON c.timestamp >= a.Zeitstempel
      GROUP BY c.timestamp)
       LEFT JOIN c ON c.timestamp = stamp1
       LEFT JOIN a ON a.Zeitstempel = stamp2;