Great explanation of table JOINS on the following picture:

http://i.stack.imgur.com/N1IGZ.jpg

Totally simple multiple UPDATE statement:

http://www.karlrixon.co.uk/writing/update-multiple-rows-with-different-values-and-a-single-sql-query/

Optimize SQL DB:

http://blog.intellisenseipt.com/sql-tips-to-speed-up-your-database/