A fix for the bug when MyISAM tmp table has to be created in order

to resolve derived table.

Will make a test case for this quite soon.

sql/sql_derived.cc

@@ -88,6 +88,7 @@ int mysql_derived(THD *thd, LEX *lex, SELECT_LEX_UNIT *unit, TABLE_LIST *t)
   
     if ((derived_result=new select_union(table)))
     {
+      derived_result->tmp_table_param=&tmp_table_param;
       unit->offset_limit_cnt= sl->offset_limit;
       unit->select_limit_cnt= sl->select_limit+sl->offset_limit;
       if (unit->select_limit_cnt < sl->select_limit)
@@ -118,7 +119,7 @@ int mysql_derived(THD *thd, LEX *lex, SELECT_LEX_UNIT *unit, TABLE_LIST *t)
 	  table->tmp_table=TMP_TABLE;
 	  if (!lex->describe)
 	    sl->exclude();
-	  t->db="";
+	  t->db=(char *)"";
 	  t->derived=(SELECT_LEX *)0; // just in case ...
 	}
       }

sql/sql_union.cc

@@ -80,6 +80,7 @@ bool select_union::send_data(List<Item> &values)
   {
     if (create_myisam_from_heap(table, tmp_table_param, info.last_errno, 0))
       return 1;
+    thd->net.report_error=0; // donno why does it work, but it does ...
   }
   return 0;
 }