SET @start_global_value = @@global.expensive_subquery_limit;
SELECT @start_global_value;
@start_global_value
100
select @@global.expensive_subquery_limit;
@@global.expensive_subquery_limit
100
select @@session.expensive_subquery_limit;
@@session.expensive_subquery_limit
100
show global variables like 'expensive_subquery_limit';
Variable_name	Value
expensive_subquery_limit	100
show session variables like 'expensive_subquery_limit';
Variable_name	Value
expensive_subquery_limit	100
select * from information_schema.global_variables where variable_name='expensive_subquery_limit';
VARIABLE_NAME	VARIABLE_VALUE
EXPENSIVE_SUBQUERY_LIMIT	100
select * from information_schema.session_variables where variable_name='expensive_subquery_limit';
VARIABLE_NAME	VARIABLE_VALUE
EXPENSIVE_SUBQUERY_LIMIT	100
set global expensive_subquery_limit=10;
set session expensive_subquery_limit=20;
select @@global.expensive_subquery_limit;
@@global.expensive_subquery_limit
10
select @@session.expensive_subquery_limit;
@@session.expensive_subquery_limit
20
show global variables like 'expensive_subquery_limit';
Variable_name	Value
expensive_subquery_limit	10
show session variables like 'expensive_subquery_limit';
Variable_name	Value
expensive_subquery_limit	20
select * from information_schema.global_variables where variable_name='expensive_subquery_limit';
VARIABLE_NAME	VARIABLE_VALUE
EXPENSIVE_SUBQUERY_LIMIT	10
select * from information_schema.session_variables where variable_name='expensive_subquery_limit';
VARIABLE_NAME	VARIABLE_VALUE
EXPENSIVE_SUBQUERY_LIMIT	20
set global expensive_subquery_limit=1.1;
ERROR 42000: Incorrect argument type to variable 'expensive_subquery_limit'
set global expensive_subquery_limit=1e1;
ERROR 42000: Incorrect argument type to variable 'expensive_subquery_limit'
set global expensive_subquery_limit="foo";
ERROR 42000: Incorrect argument type to variable 'expensive_subquery_limit'
SET @@global.expensive_subquery_limit = @start_global_value;
SELECT @@global.expensive_subquery_limit;
@@global.expensive_subquery_limit
100