set @@session.max_heap_table_size=16*1024*1024;
create table t1 select * from information_schema.session_status where variable_name like 'Opened%';
create temporary table t2 (a int) engine=memory;
select variable_name, session_status.variable_value - t1.variable_value
from information_schema.session_status join t1 using (variable_name);
variable_name	session_status.variable_value - t1.variable_value
OPENED_FILES	0
OPENED_PLUGIN_LIBRARIES	0
OPENED_TABLE_DEFINITIONS	2
OPENED_TABLES	1
OPENED_VIEWS	0
truncate table t2;
select variable_name, session_status.variable_value - t1.variable_value
from information_schema.session_status join t1 using (variable_name);
variable_name	session_status.variable_value - t1.variable_value
OPENED_FILES	0
OPENED_PLUGIN_LIBRARIES	0
OPENED_TABLE_DEFINITIONS	2
OPENED_TABLES	1
OPENED_VIEWS	0
drop table t1;