The exists rollup type populates with a true/false value based on any related record of the type meeting the rollup conditions. Similar terms to describe this rollup type are any or has

In this first section of the form when creating an exists rollup, the calculation type of rollup must be entered, before the selecting exists as the rollup type. As usual the table and column to populate are also entered

This example below will populate a column on case records specifying if a knowledge article has been linked to the case. An example like this could be used to enforce a knowledge article being linked to the case before it is resolved without having to write bespoke custom code

The next section contains details for the related record. This example specifies to use the knowledge article and case intersect table and to only count active records which relate the article. The No Lock option can also be set for a minor performance improvement, but will remove enforcing of transactional integrity in the rollup calculations

This view shows the example exists rollup where one of the cases has a linked article, bit the other doesn’t