Alter a table column with auto increment by 1 in derby
To alter the column to be auto-generated, the code is
ALTER TABLE ISSUERECIPT ALTER IRCODE SET INCREMENT BY 1;BUT the column must already be defined with the IDENTITY attribute (as written in this documentation).
In most cases (assuming that you too), the primary key column is not set as IDENTITY. Therefore, you may intend to alter the column to IDENTITY, but that is impossible.
The only way is to drop the table and create it again, as written here.