1. How do you show the currently running queries? – SHOW FULL PROCESSLIST;
2. How do you kill a MySQL query? – See the ID of it from the question above, then KILL id. You can separate multiple IDs by space.
3. I need to find out how many client connections were aborted by MySQL server. – It’s displayed in SHOW STATUS query, alternatively accessible via mysqladmin extended-status.
4. What does SET SQL_AUTO_IS_NULL =1 do? – you can find the last inserted row for a table that contains an AUTO_INCREMENT column by issuing WHERE auto_increment_column IS NULL