Update Database on Plugin update

Hi,

I have an issue with my plugin and I would be very thankful if somebody here could help me.

Plugin version 1.0.2 create a table with 2 columns in the blog’s DB. I know… I should have used wordpress tables but I thought this was the best solution for me at the time.

Now, with version 1.1.0 I need a third column in that table.

Is there a hook, or an action or something that is triggered when the plugin is updated? So I could write some ‘alter table add column balablaa…’ code in my plugin when it is updated from some older version?

Thak You very much!