For processing SELECT queries MySQL needs some times the help of temporary tables. These temporary tables can be created either in memory or on disk.
The number of creations of such temporary tables can be found with the following command:
mysql> SHOW GLOBAL STATUS LIKE 'created_tmp%tables';
+-------------------------+-------+
| Variable_name | Value |
+-------------------------+-------+
| Created_tmp_disk_tables | 4 |
| Created_tmp_tables | 36 |
+-------------------------+-------+ …
