Does index rebuild on Insert/Update?

[holly]

I just discovered how to make an index on my MySQL database, which vastly speeds up my query speed - hurray! So here\'s a really basic question I can\'t see an answer to in the MySQL manual - when I add another chunk of data to my table, via INSERT, or change data via UPDATE, are the indexes I\'ve created rebuilt automatically? From what I\'ve read, it sounds like they are, but I\'m not sure.

 

If the index updates automatically, then performance-wise, is it faster to DROP and recreate the index when updating rather than let it update automatically? Table has around 200K records in it, if that matters.

 

thanks,

Holly