--- url: >- /statelake/administering-statelake/designer/data-definitions/file-definitions/flat-file-definitions/design-flat-file-definitions/file-dataview-link-drag-and-drop-flat-file-definitions.md --- # File Dataview - Link Drag-and-drop - Flat File Definitions The primary, fastest, and probably cleanest way of creating and maintaining a **Link** between the dataviews, is by the use of the drag-and-drop method. There is no **Link** tab within the definition itself, so any **Link** needs to be forged on the designer canvas. There is another alternate way to create and maintain a **Link** through the **Link** button which is discussed in [File Dataview - Link Button - Flat File Definitions](/statelake/administering-statelake/designer/data-definitions/file-definitions/flat-file-definitions/design-flat-file-definitions/file-dataview-link-button-flat-file-definitions). ::: info Every dataview that is created will have two (**2**) additional fields automatically generated and inserted into the dataview by **Statelake**, to enhance and support the building of any dataview relationships. These internal-use only fields are called **ID** and **MASTER_ID**, and are not included any mapping process. ::: ::: info While in theory you can link any field in one dataview to any field in any other dataview, it is usual to only link a **MASTER_ID** of one dataview into the **ID** of the dataview being linked into. ::: So for instance, you would **Link** the **MASTER_ID** of an invoice lines dataview into the **ID** of a dataview for the invoice headers. Or you would **Link** the **MASTER_ID** of a dataview holding contact names and details into the **ID** of a dataview holding the company information - and not vice-versa. In an imaginary space we have a list of neighbours in one dataview and a list of names with nicknames in a second dataview. The **NEIGHBOURS** dataview is the top-level, and **FRIENDS** will be linked into it. To add this **Link** relationship, the **MASTER_ID** field from the **FRIENDS** dataview will be dropped onto the **ID** field of the dataview **NEIGHBOURS**. Click on **FRIENDS.MASTER_ID**, and drag it so that the label shows as per the example, then unclick to drop it. The label should read “Link detail **FRIENDS.MASTER_ID** to master **NEIGHBOURS.ID**”. You will see the label change to this as soon as the tip of your pointer lands on the **ID** field of **NEIGHBOURS**. Once released, three ( **3** ) things will happen. * The **FRIENDS** dataview will be re-named to **FRIENDS linked to NEIGHBOURS**, * A one‑to‑many relationship link line and symbol will appear between the two dataviews - the one “single” link pointing at **ID** in **NEIGHBOURS**, and the “many” pointing at **MASTER_ID** in the renamed dataview **FRIENDS linked to NEIGHBOURS**. This link line is not placed exactly on the fields, but will appear at the top of the items that are linked. * And **ID** in **NEIGHBOURS** will be bolded, as will **MASTER_ID** in **FRIENDS** - to indicate the fields that are linked. The link between the two datasets has now been successfully completed. ::: info The colours of the link lines have no meaning. They are random and arbitrary. The colours of the link lines may be different every time that the definition is opened and the dataviews are viewed on the designer canvas. ::: You can edit the link by double-clicking on the link line, which will open an editing window. For information about this window, please review [File Dataview - Link Button - Flat File Definitions](/statelake/administering-statelake/designer/data-definitions/file-definitions/flat-file-definitions/design-flat-file-definitions/file-dataview-link-button-flat-file-definitions). Columns and window borders can be resized as required by dragging them with the mouse. Close the definition canvas by selecting **Close** from the **File** menu. You will return to the **File Definition** window. Click **Save** to save and close the module. Always remember to select SAVE here – else all of your hard work linking these datasets will not be saved.