MySQL: Killing connections massively - Userlinux.net

Every so often I run into situation when I need to kill a lot of connections on MySQL server - for example hundreds of instances of some bad query is running making server unusable. Many people have special scripts which can take the user, source host or query as a parameter and perform the action. There is also a way to do it just using MySQL with a few commands:

mysql> SELECT concat('KILL ',id,';') FROM information_schema.processlist WHERE user='root';
+------------------------+
| concat('KILL ',id,';') 
+------------------------+
| KILL 3101;			 
| KILL 2946;			 
+------------------------+
2 rows IN SET (0.00 sec)
mysql> SELECT concat('KILL ',id,';') FROM information_schema.processlist WHERE user='root' INTO OUTFILE '/tmp/a.txt';
Query OK, 2 rows affected (0.00 sec)
mysql> source /tmp/a.txt;
Query OK, 0 rows affected (0.00 sec)

Fully copypasted from MySQL Performance Blog.