Linked Fields are a special Data Type that automatically pulls the values in the fields from one table, called "source table", into another table, called "target table". Linked Fields help avoid duplication and ensure that Records dynamically reflect any changes that occurred in other places within the infrastructure. Let's consider an example.
Imagine you have a Vendor table that holds records for each of your vendors; a People table that holds the employees at your company, vendor contacts, and other outside contacts; and a Contract table holding information about your contracts.
Within a contract record, you will typically pull in and display fields from the vendor record for the contract’s vendor, the names and email addresses of the main vendor contacts, and information about your own employees who are responsible for the contract.
Within the vendor record, you might also show a Related Table of all contracts for that vendor, which links to the Contract table, as well as a Related Table of all vendor contacts, which links to the People table.
Linked Fields can be configured to automatically update when the value in the source table changes or to save the old value. In either case, they retain the display attributes, permissions, and size restrictions of the source fields. You can copy or link fields from another record in the current table, another table within the current KnowledgeBase or even an external database. Fields that have been linked from another table are marked as "Link to" in the data type column at Setup > Tables > select Table to edit > Fields.
Several different kinds of Linked fields appear at the bottom of the "New" drop-down on the Fields tab in the Table wizard at Setup > Tables > select Table to edit > Fields.
- Link to single field. Links to one field in another table. Seldom used because you will often find you want to add more fields later and have to redo it.
- Link to selected fields. The most common way to pull in fields from a single record in another table, for example user information in a case or asset. Can also be used to pull in multiple fields from records as part of a multi-to-multi relationship. In this case it is displayed as an embedded table rather than as separate fields.
- Link to all fields. Pulls all fields in and if new fields are added to source table they are automatically added to the set of target fields.
- Single field from multiple tables. Used for the Assigned To fields to allow an issue to be assigned to a Team or an individual and for other situations in which a single field should display values from more than one table.
- Related table. Shows one of the above relationships from the other direction. For example, when the Assigned To field is used to assign each Issue to a user, a Related table shows all the Issues that were assigned to her.