How can I do an update to a table where I dont want to allow records to have
a field(s) which occur in another record, whenm each record has a unique
integer id. For example, suppose I have a table setup as:

       "id INTEGER(11) PRIMARY KEY NOT NULL AUTO_INCREMENT," +
       "activities_id INTEGER(11)," +
       "sombody VARCHAR(60),"+
       "something VARCHAR(255),"+

and I have a record I want to INSERT to this table, but only if, say, there
is not already a record there that has both 'somebody' and 'activities_id'
in the table already.

Is there an expeditious way to do this, without examining each record in the
table? Thank you, Ike