Find out slow sql of mysql

Find out slow sql of mysql   Recent days, I should do a sql tuning for a mysql database, and I know a bit of mysql db. In order to find the slow sql, i do the slow_query_log on to collect the slow sql.  

[sql]
mysql> show variables like 'slow%';  
+---------------------+-------------------------------------------+  
| Variable_name       | Value                                     |  
+---------------------+-------------------------------------------+  
| slow_launch_time    | 2                                         |  
| slow_query_log      | ON                                        |  
| slow_query_log_file | /opt/mysql_data/mysql/mysql-test-slow.log |  
+---------------------+-------------------------------------------+  
3 rows in set (0.00 sec)  
  
mysql> set global slow_launch_time=5;  
Query OK, 0 rows affected (0.00 sec)  
  
mysql> show variables like 'slow%';  
+---------------------+-------------------------------------------+  
| Variable_name       | Value                                     |  
+---------------------+-------------------------------------------+  
| slow_launch_time    | 5                                         |  
| slow_query_log      | ON                                        |  
| slow_query_log_file | /opt/mysql_data/mysql/mysql-test-slow.log |  
+---------------------+-------------------------------------------+  
3 rows in set (0.00 sec)  
We can read  /opt/mysql_data/mysql/mysql-test-slow.log  to find slow sql.