To delete a table relationship
If the tables that participate in the table relationship are open, close them. You cannot delete a table relationship between open tables.
On the Database Tools tab, in the Show/Hide group, click Relationships.
If the tables that participate in the table relationship are not visible, on the Design tab, in the Relationships group, click Show Table. Then select the tables to add in the Show Table dialog box, click Add, and then click Close.
Click the table relationship line for the table relationship that you want to delete (the line becomes bold when it is selected), and then press the DELETE key.
On the Design tab, in the Relationships group, click Close.
In the Navigation Pane, right click the table in which you want to remove the primary key and then click Design View.
Click the row selector for the current primary key.
If the primary key consists of a single field, click the row selector for that field.
If the primary key consists of multiple fields, click the row selector for any field in the primary key.
On the Design tab, in the Tools group, click Primary Key.
The key indicator is removed from the field or fields that you previously specified as the primary key.
To add an AutoNumber primary key
When you create a new table in Datasheet view, Access automatically creates a primary key for you and assigns it the AutoNumber data type. If you have an existing table to which you want to add a primary key field, however, you must open the table in Design view.
In the Navigation Pane, right click the table to which you want to add the primary key and then click Design View.
Locate the first available empty row in the table design grid.
In the Field Name column, type a name, such as CustomerID.
In the Data Type column, click the drop-down arrow and click AutoNumber.
Under Field Properties, in New Values, click Increment to use incremental numeric values for the primary key, or click Random to use random numbers.