SELECT @@global.optimizer_trace_offset; @@global.optimizer_trace_offset -1 SET @@global.optimizer_trace_offset=5; show global variables like 'optimizer_trace_offset'; Variable_name Value optimizer_trace_offset 5 select * from information_schema.global_variables where variable_name='optimizer_trace_offset'; VARIABLE_NAME VARIABLE_VALUE OPTIMIZER_TRACE_OFFSET 5 select @@session.optimizer_trace_offset; @@session.optimizer_trace_offset -1 show session variables like 'optimizer_trace_offset'; Variable_name Value optimizer_trace_offset -1 select * from information_schema.session_variables where variable_name='optimizer_trace_offset'; VARIABLE_NAME VARIABLE_VALUE OPTIMIZER_TRACE_OFFSET -1 set session optimizer_trace_offset=10; select @@session.optimizer_trace_offset; @@session.optimizer_trace_offset 10 show session variables like 'optimizer_trace_offset'; Variable_name Value optimizer_trace_offset 10 set session optimizer_trace_offset=0; select @@session.optimizer_trace_offset; @@session.optimizer_trace_offset 0 show session variables like 'optimizer_trace_offset'; Variable_name Value optimizer_trace_offset 0 set session optimizer_trace_offset=-100; select @@session.optimizer_trace_offset; @@session.optimizer_trace_offset -100 show session variables like 'optimizer_trace_offset'; Variable_name Value optimizer_trace_offset -100 set session optimizer_trace_offset=2000000000; select @@session.optimizer_trace_offset; @@session.optimizer_trace_offset 2000000000 show session variables like 'optimizer_trace_offset'; Variable_name Value optimizer_trace_offset 2000000000 set session optimizer_trace_offset=-2000000000; select @@session.optimizer_trace_offset; @@session.optimizer_trace_offset -2000000000 show session variables like 'optimizer_trace_offset'; Variable_name Value optimizer_trace_offset -2000000000 set session optimizer_trace_offset=default; select @@session.optimizer_trace_offset; @@session.optimizer_trace_offset 5 show session variables like 'optimizer_trace_offset'; Variable_name Value optimizer_trace_offset 5 set global optimizer_trace_offset=default; select @@global.optimizer_trace_offset; @@global.optimizer_trace_offset -1 show global variables like 'optimizer_trace_offset'; Variable_name Value optimizer_trace_offset -1 set optimizer_trace_offset=1.1; ERROR 42000: Incorrect argument type to variable 'optimizer_trace_offset' set optimizer_trace_offset="foobar"; ERROR 42000: Incorrect argument type to variable 'optimizer_trace_offset'