I would like to change a column in a table from NULLable to NOT NULL.

From looking at the Interbase 6 SQL Reference, and searching for help on the
internet, it would appear you cannot do this.

Is the only way to do this is to create a new column as not null, copy the
field data from the old column to the new column, delete the old column and
rename the new column to the old column name?

If there is a way you can use ALTER TABLE..... please let me know. If not
could you confirm that the above is true?

Thanks,
Stephen