select @@global.debug_sync;
ERROR HY000: Variable 'debug_sync' is a SESSION variable
select @@session.debug_sync;
@@session.debug_sync
ON - signals: ''
show global variables like "debug_sync";
Variable_name	Value
show session variables like "debug_sync";
Variable_name	Value
debug_sync	ON - signals: ''
select * from information_schema.global_variables where variable_name="debug_sync";
VARIABLE_NAME	VARIABLE_VALUE
select * from information_schema.session_variables where variable_name="debug_sync";
VARIABLE_NAME	VARIABLE_VALUE
DEBUG_SYNC	ON - signals: ''
set @@session.debug_sync=1;
ERROR 42000: Incorrect argument type to variable 'debug_sync'
set @@session.debug_sync=1.1;
ERROR 42000: Incorrect argument type to variable 'debug_sync'
set @@session.debug_sync=1e1;
ERROR 42000: Incorrect argument type to variable 'debug_sync'