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  1. Just because the database can perform an operation, does not mean it's efficient. ORDER BY RAND() for example. There are better code ways!
  2. Verifying MySQL db schema's in dev/test/prod or large replication topologies made easier with Schema Sync - http://schemasync.org
  3. If you want to poll a large network for any MySQL servers, try polling the default port $nc -z hostname 3306 $?=0 indicates open MySQL port
  4. Plenty of great MySQL and MySQL related content being discussed at http://opensqlcamp.org in Portland #opensqlcamp
  5. skip-name-resolve is a valuable parameter to know about. Eliminating DNS lookups can improve performance. http://bit.ly/skip_name_res...
  6. SHOW PROCESSLIST can also provide valuable host stats. You should monitor per host connections,sleeping,max sleeping and >95pct sleep.
  7. Know the different states in the SHOW PROCESSLIST that affect your performance. This article provides a good overview. http://bit.ly/mf285
  8. The SHOW FULL PROCESSLIST provides a snapshot of current SQL activity.While not a complete transaction view, valuable info can be determined
  9. EXPLAIN is an essential tool for MySQL developers. Check out this detailed presentation -- http://www.slideshare.net/l...
  10. If you don't know what QEP means,if you don't use or know how to interpret EXPLAIN output,now is the time to start. An essential MySQL tool.
  11. How consistent is your replication environment at crash time? innodb_support_xa, sync_binlog are two important and often unset variables
  12. A very neat and simple 1 line command to determine per table INSERT/UPDATE/DELETE statistics on your server -- http://tr.im/mysql_dml_stats
  13. The amount of Innodb auto recovery can be calculated with 'Log flushed up to' - 'Last checkpoint at'.Found in LOG part of SHOW INNODB STATUS
  14. Innodb does perform an automatic recovery on MySQL restart. The factors of how long include current load and innodb_log_file_size*group.
  15. MyISAM does not perform automatic data recovery after a mysqld/server crash. A common option used is --myisam-recover=FORCE,BACKUP
  16. Correct @chuckh1958, a partial index is the left most portion of a given character column. Read more at http://tr.im/mysql_index_types
  17. Understanding Different MySQL Index Implementations. Read more at http://tr.im/mysql_index_types
  18. Do you know the difference between single column indexes, concatenated indexes,covering indexes and partial indexes.Each affect performance.
  19. Be sure to check out @MySQL_Librarian for a good collection of valuable reference and reading material. -- http://tr.im/mysql_librarian
  20. What is your DR plan for disk full? Be sure to include MySQL binlog partition full in your scenarios. See http://tr.im/mysqlbinlogfull