SET @start_global_value = @@global.userstat;
select @@global.userstat = 0 or @@global.userstat = 1;
@@global.userstat = 0 or @@global.userstat = 1
1
select @@session.userstat;
ERROR HY000: Variable 'userstat' is a GLOBAL variable
SET @@global.userstat=0;
show global variables like 'userstat';
Variable_name	Value
userstat	OFF
show session variables like 'userstat';
Variable_name	Value
userstat	OFF
select * from information_schema.global_variables where variable_name='userstat';
VARIABLE_NAME	VARIABLE_VALUE
USERSTAT	OFF
select * from information_schema.session_variables where variable_name='userstat';
VARIABLE_NAME	VARIABLE_VALUE
USERSTAT	OFF
set global userstat=ON;
select @@global.userstat;
@@global.userstat
1
set global userstat=OFF;
select @@global.userstat;
@@global.userstat
0
set global userstat=1;
select @@global.userstat;
@@global.userstat
1
set session userstat=1;
ERROR HY000: Variable 'userstat' is a GLOBAL variable and should be set with SET GLOBAL
set global userstat=1.1;
ERROR 42000: Incorrect argument type to variable 'userstat'
set global userstat=1e1;
ERROR 42000: Incorrect argument type to variable 'userstat'
set global userstat="foo";
ERROR 42000: Variable 'userstat' can't be set to the value of 'foo'
SET @@global.userstat = @start_global_value;