SET @start_global_value = @@global.old_alter_table;
SELECT @start_global_value;
@start_global_value
0
select @@global.old_alter_table;
@@global.old_alter_table
0
select @@session.old_alter_table;
@@session.old_alter_table
0
show global variables like 'old_alter_table';
Variable_name	Value
old_alter_table	OFF
show session variables like 'old_alter_table';
Variable_name	Value
old_alter_table	OFF
select * from information_schema.global_variables where variable_name='old_alter_table';
VARIABLE_NAME	VARIABLE_VALUE
OLD_ALTER_TABLE	OFF
select * from information_schema.session_variables where variable_name='old_alter_table';
VARIABLE_NAME	VARIABLE_VALUE
OLD_ALTER_TABLE	OFF
set global old_alter_table=1;
set session old_alter_table=ON;
select @@global.old_alter_table;
@@global.old_alter_table
1
select @@session.old_alter_table;
@@session.old_alter_table
1
show global variables like 'old_alter_table';
Variable_name	Value
old_alter_table	ON
show session variables like 'old_alter_table';
Variable_name	Value
old_alter_table	ON
select * from information_schema.global_variables where variable_name='old_alter_table';
VARIABLE_NAME	VARIABLE_VALUE
OLD_ALTER_TABLE	ON
select * from information_schema.session_variables where variable_name='old_alter_table';
VARIABLE_NAME	VARIABLE_VALUE
OLD_ALTER_TABLE	ON
set global old_alter_table=1.1;
ERROR 42000: Incorrect argument type to variable 'old_alter_table'
set global old_alter_table=1e1;
ERROR 42000: Incorrect argument type to variable 'old_alter_table'
set global old_alter_table="foo";
ERROR 42000: Variable 'old_alter_table' can't be set to the value of 'foo'
SET @@global.old_alter_table = @start_global_value;
SELECT @@global.old_alter_table;
@@global.old_alter_table
0