[SQLObject] Setting Conditions in a Table

[luis c. <lo....@gm...>]

Is it possible to set conditions on a table entry?  For example, if you have
a data set with these cols:

ts  = DateTimeCol () // time stamp
id_str = StringCol // string identifier

Can I create a condition that forces the ts/id_str combination within each
row to be unique?

Thanks!

- Luis