The table consists of 3 fields: EVENTDATE, EVENTTYPE, EVENTKEY. All 3
fields are used in the combined primary table index.
I am trying to delete the EVENTTYPE field, however Firebird does not
allow for this. How to get rid of this field and change the primary
index to consist of the two remaing fields only ? I cannot delete and
recreate the table, as it already contains data.

note: the original command to create the primary index was:
ALTER TABLE GH ADD PRIMARY KEY (EVENTDATE, EVENTTYPE, EVENTKEY);