In OBSERVATION table in CDM V6, there is a column called observation_event_id. The name implies it is an observation_id. But it is not. it can be any event id except observation event id. In Wiki, it states “A foreign key to an event table (e.g., PROCEDURE_OCCURRENCE_ID).”
The practical use of this field is to link SURVEY_CONDUCT table, in which case, it would be survey_conduct_id. Another usage of this field is to link OBSERVATION table to EPISODE table in Oncology Extension model, in which case, it would be episode_id. In neither cases, it is an observation event id.
I think it should be changed to some other names, e.g.,
This is also true for another column name in this table obs_event_field_concept_id. Both names are misleading.
Some relevant post is here