When you do LEFT JOIN ower several tables (in my case 7) and when (at 
least i think) one of them contains no rows at all, mysql gets: 

ERROR 2013: Lost connection to MySQL server during query

and to mysql error log appears :
mysqld process hanging, pid 7198 - killed
001207 19:03:31  mysqld restarted
/usr/libexec/mysqld: ready for connections

HERE is my sql query:
select distinct tootaja.uid as tootid, broneering.uid as bronid, 
broneeritud_objekt.uid as bronobid, teenus.uid as teenid, 
teenusepakett.uid as tpakkid, SUM(teenus.hind) as thind, SUM
(teenus_teenusepakett.hind) as tphind, teenus.ajakulu as tkulu, 
teenusepakett.ajakulu as tpkulu from tootaja left join broneering on 
tootaja.uid=broneering.tootaja_id left join broneeritud_objekt on 
broneering.uid=broneeritud_objekt.broneering_id left join teenus on 
broneeritud_objekt.teenus_id=teenus.uid left join teenusepakett on 
broneeritud_objekt.teenusepakett_id=teenusepakett.uid left join 
teenus_teenusepakett on 
teenusepakett.uid=teenus_teenusepakett.teenusepakett_id left join 
teenus_teenusepakett as ttpp on teenus.uid=ttpp.teenus_id where 
tootaja.uid=1 and broneering.uid=1 group by broneeritud_objekt.uid;

AND WHERE all the tables contained at least 1 row ecxept one 
(teenusepakett)
mysql> select count(*) from teenusepakett;
+----------+
| count(*) |
+----------+
|        0 |
+----------+