DELETE FROM TRANSACTION_EVENT WHERE TRANSACTION_EVENT_ID = 1;
DELETE FROM TRANSACTION_EVENT WHERE TRANSACTION_EVENT_ID = 2;
--The event below is referenced from TRANSACTION like last transaction event, but there is no error
DELETE FROM TRANSACTION_EVENT WHERE TRANSACTION_EVENT_ID = 3;
DELETE FROM TRANSACTION WHERE TRANSACTION_ID = 1;

DELETE FROM TRANSACTION_EVENT WHERE TRANSACTION_EVENT_ID = 1;
DELETE FROM TRANSACTION_EVENT WHERE TRANSACTION_EVENT_ID = 2;
--Shallow update: All foreign keys set to NULL. SQL error appears here since there is some non-nullable foreign keys
UPDATE TRANSACTION SET LAST_TRANSACTION_EVENT_ID = NULL, CURRENCY_ID = NULL WHERE TRANSACTION_ID = 1;
DELETE FROM TRANSACTION_EVENT WHERE TRANSACTION_EVENT_ID = 3;
DELETE FROM TRANSACTION WHERE TRANSACTION_ID = 1;

protected void writeFromObjectIntoRowInternal(Object object, AbstractRecord databaseRow, AbstractSession session, ShallowMode mode) {
        List<DatabaseField> foreignKeyFields = getForeignKeyFields();
        if (mode != null) {
            List<DatabaseField> nonNullableFields = null;
            for (DatabaseField field : foreignKeyFields) {
                if (field.isNullable()) {
                    if (mode == ShallowMode.Insert) {
                        // add a nullable field with a null value
                        databaseRow.add(field, null);
                    }
                } else {
                    if (nonNullableFields == null) {
                        nonNullableFields = new ArrayList<DatabaseField>();
                    }
                    nonNullableFields.add(field);
                }
            }