Knowledge Base



KB10258 - ADO join check list.

Check list for proper ADO joining:

  • Joining a shape file to an external database requires a one-to-one relation.
  • ​Identifiers in a coverage must be unique, integer, and never empty.
  • ​It is recommended that a coverage be sorted by an identifier (ADOPrimary field) and the same order applied in the external database (ADOSecondary field). This speeds up a join operation dramatically.
  • ​If a query is based on an identifier (ADOSecondary) in the external database that is not unique, only the first matching record will be used. We strongly recommend avoiding this situation.
  • ​If a join is not possible, joining will turn off automatically. To turn it on again, reapply the ADOJoin, ADOPrimary, or ADOSecondary parameter.
Created: November 21, 2003, Modified: December 29, 2015