mysql -u root -p

SHOW VARIABLES LIKE 'slow_query_log';

SHOW VARIABLES LIKE 'slow_query_log_file';

SHOW VARIABLES LIKE 'long_query_time';

SET GLOBAL slow_query_log = 'ON';

SET GLOBAL slow_query_log_file = '/path/filename';

typically, the slow query log file is located at /var/lib/mysql/{hostname}-slow.log.

SELECT SLEEP(X);

test whether slow query log is working

SET GLOBAL slow_query_log = 'OFF';

turn off slow query log when you are done troubleshooting