SET @start_global_value = @@global.max_join_size;
SELECT @start_global_value;
@start_global_value
18446744073709551615
select @@global.max_join_size;
@@global.max_join_size
18446744073709551615
select @@session.max_join_size;
@@session.max_join_size
18446744073709551615
show global variables like 'max_join_size';
Variable_name	Value
max_join_size	18446744073709551615
show session variables like 'max_join_size';
Variable_name	Value
max_join_size	18446744073709551615
select * from information_schema.global_variables where variable_name='max_join_size';
VARIABLE_NAME	VARIABLE_VALUE
MAX_JOIN_SIZE	18446744073709551615
select * from information_schema.session_variables where variable_name='max_join_size';
VARIABLE_NAME	VARIABLE_VALUE
MAX_JOIN_SIZE	18446744073709551615
set global max_join_size=10;
set session max_join_size=20;
select @@global.max_join_size;
@@global.max_join_size
10
select @@session.max_join_size;
@@session.max_join_size
20
show global variables like 'max_join_size';
Variable_name	Value
max_join_size	10
show session variables like 'max_join_size';
Variable_name	Value
max_join_size	20
select * from information_schema.global_variables where variable_name='max_join_size';
VARIABLE_NAME	VARIABLE_VALUE
MAX_JOIN_SIZE	10
select * from information_schema.session_variables where variable_name='max_join_size';
VARIABLE_NAME	VARIABLE_VALUE
MAX_JOIN_SIZE	20
set global max_join_size=1.1;
ERROR 42000: Incorrect argument type to variable 'max_join_size'
set global max_join_size=1e1;
ERROR 42000: Incorrect argument type to variable 'max_join_size'
set global max_join_size="foo";
ERROR 42000: Incorrect argument type to variable 'max_join_size'
select @@sql_big_selects;
@@sql_big_selects
0
set max_join_size=cast(-1 as unsigned int);
Warnings:
Note	1105	Cast to unsigned converted negative integer to it's positive complement
select @@sql_big_selects;
@@sql_big_selects
1
set max_join_size=100;
select @@sql_big_selects;
@@sql_big_selects
0
SET @@global.max_join_size = @start_global_value;
SELECT @@global.max_join_size;
@@global.max_join_size
18446744073709551615