This step is displayed when there are no predefined table relationships for the new table being added to your query or when there is more than one redefined relationship but you decided to define your own.
Table relationships are defined by identifying columns in the new table that represent the same data as columns in one of the tables already part of your query. For any given row in your query results, only the rows from the new table where these columns match will be included.
When defining a new table relationship, keep in mind one-to-many and many-to-one relationships between the rows in your tables. Avoid creating a relationship that is ambiguous and would result in a many-to-many relationship because this can result in your query returning a substantial number of rows containing repetitive information. A good practice is to know what the Primary Key is of the new table you are adding. Then define the relationship based on relating columns in one of the other tables to the Primary Key columns of the new table. The result is that for any given row in your query results, only zero or one rows from the new table will be related (a many-to-one relationship). This is similar in concept to a DBLookup or VLookup function.
Table to base relationship on
Click the drop-down to select from one of the tables that is already part of your query. The table you select would be the table that contains the columns that relate to columns in the new table (such as the columns that contain the new table's Primary Key values).
Add
Click to display the Add Column Relationship window.
Edit
Click to display the Edit Column Relationship window.
Remove
Click to remove the currently selected column relationship.