Table vs. CRSPAccess Usage Notes
The Link Actions table includes the primary identifiers for the databases: GVKEY for CCM and PERMNO for CRSP Stock. In a standalone setup where data are dumped and stored as a table these identifiers are included in each table and used to join data.
CRSPAccess programming access always organizes all data for one GVKEY (CCM) or PERMNO (CRSP Stock) in a single structure. The primary identifier is set at the full structure level and inherited by all substructures. Therefore the field is not explicitly included in the substructures. When a CCM composite record is built by the crsp_ccm_read_all function the primary identifier becomes the PERMNO used as the key, which is stored in the CCM_ID field of this structure. The LOADTYPE flag is set to 1 to signify that the structure is loaded with a composite record.