FQL is a query language that allows you to retrieve, filter and project data from any data source containing FHIR Resources. It brings the power of three existing languages together: SQL, JSON and FhirPath. It allows you to create tables and is useful for gaining insight and perform quality control.
This code system https://fhir.kbv.de/CodeSystem/KBV_CS_SFHIR_ITA_WOP defines the following codes: