Manuals are your friend, read them.
http://www.mysql.com/documentation/mysql/bychapter/manual_Problems.html#IDX1399
This error occurs in older MySQL versions when an in-memory temporary table becomes larger than tmp_table_size bytes. To avoid this problem, you can use the -O tmp_table_size=# option to
mysqld to increase the temporary table size or use the SQL option SQL_BIG_TABLES before you issue the problematic query. See section 7.33 SET Syntax.
You can also start mysqld with the --big-tables option. This is exactly the same as using SQL_BIG_TABLES for all queries.
In MySQL Version 3.23, in-memory temporary tables will automatically be converted to a disk-based MyISAM table after the table size gets bigger than tmp_table_size.
