mysqld got signal 6; This could be because you hit a bug. It is also possible that this binary or one of the libraries it was linked against is corrupt, improperly built, or misconfigured. This error can also be caused by malfunctioning hardware. We will try our best to scrape up some info that will hopefully help diagnose the problem, but since we have already crashed, something is definitely wrong and this may fail. key_buffer_size=16777216 read_buffer_size=131072 max_used_connections=1 max_connections=100 threads_connected=1 It is possible that mysqld could use up to key_buffer_size + (read_buffer_size + sort_buffer_size)*max_connections = 233983 K bytes of memory Hope that's ok; if not, decrease some variables in the equation. thd=0x8c70fc0 Attempting backtrace. You can use the following information to find out where mysqld died. If you see no messages after this, something went terribly wrong... Cannot determine thread, fp=0x46ad99bc, backtrace may not be correct. Stack range sanity check OK, backtrace follows: 0x8164593 0xffffe420 (nil) 0x4033b9b3 0x4033c3db 0x40282441 0x46ab6e82 0x8100b80 0x80f9f2b 0x80fb8d7 0x8177150 0x815622b 0x8180700 0x81813ad 0x8181d07 0x81828c2 0x4018a374 0x4039218a New value of fp=(nil) failed sanity check, terminating stack trace! Please read http://dev.mysql.com/doc/mysql/en/Using_stack_trace.html and follow instructions on how to resolve the stack trace. Resolved stack trace is much more helpful in diagnosing the problem, so please do resolve it Trying to get some variables. Some pointers may be invalid and cause the dump to abort... thd->query at 0x8c8d750 = SELECT avgcost(test1.field1, test1.field3) FROM test1, test2 WHERE test2.field2 = test1.field2 GROUP BY test1.field2 thd->thread_id=1 The manual page at http://www.mysql.com/doc/en/Crashing.html contains information that should help you find out what is causing the crash.