CONCEPT_ID (to NULL or not to NULL)

[ericaVoss]

TYPE	NOTES
ITEM	When should CONCEPT_ID be NULL and when should it be 0?
FORUM POST	http://forums.ohdsi.org/t/concept-id-to-null-or-not-to-null-themis-wg3/3965/46
SOLUTION	Foreign key into the Standardized Vocabularies (i.e. the standard_concept attribute for the corresponding term is true), which serves as the primary basis for all standardized analytics. For example, condition_concept_id = 31967 contains reference value for SNOMED concept of 'Nausea'. Set the value to 0 'No matching concept' when a mapping to a standard concept cannot be found (except for MEASUREMENT/OBSERVATION.VALUE_AS_CONCEPT_ID, MEASUREMENT/OBSERVATION.UNIT_CONCEPT_ID, MEASUREMENT.OPERATOR_CONCEPT_ID which can be NULL if data does not contain a value).
NEXT STEPS	1) Submit recommendation to the CDM WG to make all CONCEPT_IDs NOT NULL columns (except for MEASUREMENT/OBSERVATION.VALUE_AS_CONCEPT_ID, MEASUREMENT/OBSERVATION.UNIT_CONCEPT_ID, MEASUREMENT.OPERATOR_CONCEPT_ID which can be NULL if data does not contain a value). 2) Update language in the WIKI under CONCEPT_ID https://github.com/OHDSI/CommonDataModel/wiki/Data-Model-Conventions