This feature describes WID tables, their history and data sources.  It attempts to describe some of the larger issues with maintaining the WID and goes beyond the scope of the structure document.  The links in the index along the right side of the page will take you to content about specific tables or types of tables.

Tables can come in four types –

Lookup Tables – these define the codes used to describe data types in data tables

Data Tables – these contain the data for various sources

Crosswalk Tables – these relate different data structures

Admin Tables – these describe the tables in the database

While Core (required) tables have complete content, non-standard (not required) tables may not.  If you have questions that are not answered by the documentation, try emailing