mysql> set profiling=1;mysql> select distinct(num) from test_test;mysql> select num from test_test group by num;mysql> show profiles;

+----------+------------+-------------------------------------

06 | Query_ID| Duration  | Query  |

08 |      1 | 0.00072550 | select distinct(num) from test_test

09 |      2 | 0.00071650 | select num from test_test group by num