id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	PRIMARY	kcu	ALL	NULL	TABLE_NAME	NULL	NULL	NULL	Using where; Open_full_table; Scanned 1 database
1	PRIMARY	rc	ALL	NULL	TABLE_NAME	NULL	NULL	NULL	Using where; Open_full_table; Scanned 1 database; Using join buffer (flat, BNL join)
1	PRIMARY	tc	ALL	NULL	TABLE_NAME	NULL	NULL	NULL	Using where; Open_full_table; Scanned 1 database; Using join buffer (incremental, BNL join)
2	UNION	kcu	ALL	NULL	TABLE_SCHEMA,TABLE_NAME	NULL	NULL	NULL	Using where; Open_full_table; Scanned 0 databases
2	UNION	tc	ALL	NULL	TABLE_NAME	NULL	NULL	NULL	Using where; Open_full_table; Scanned 1 database; Using join buffer (flat, BNL join)
NULL	UNION RESULT	<union1,2>	ALL	NULL	NULL	NULL	NULL	NULL	Using filesort