Which parameter lets you specify the datagroup for caching policy in a derived table?

The parameter that allows you to specify the datagroup for caching policy in a derived table is the datagroup_trigger. This parameter is crucial for controlling when the cache for a derived table is refreshed based on the specified datagroup's criteria. By linking a derived table to a datagroup, you ensure that the table's data is re-queried and updated according to the defined triggers in the datagroup, which can be time-based or event-based.

Using the datagroup_trigger effectively allows developers to maintain data freshness and accuracy in their Looker reports and dashboards. When a derived table is associated with a datagroup, Looker will check the conditions of that datagroup to determine if the cache should be invalidated or refreshed, thus playing a critical role in the overall caching strategy within Looker.

On the other hand, the other options like cache_policy, cache_trigger, and persistence_method serve different purposes unrelated to specifically linking a derived table's caching behavior to a datagroup.