This error happens when key column value is NULL. You need to choose
another column as key column.
Note:
Key column is the database column which lets you query each table row
individually and modify each row without altering other rows in the
same table. The values that compose a key column are unique; no two
values are the same.
Note:
Key column is the database column which lets you query each table row
individually and modify each row without altering other rows in the
same table. The values that compose a key column are unique; no two
values are the same.