Available with Standard or Advanced license.
Relationship classes help ensure referential integrity. For example, the deletion or modification of one feature could delete or alter a related feature. Furthermore, a relationship class is stored in the geodatabase, which makes it accessible to anyone who uses the geodatabase.
On-the-fly relationships, also called relates, are defined as a property of an ArcMap layer. Use them for improved editing performance.
Joins are best suited for labeling and symbology. You define joins through the relational database to make standard SQL queries cross the database as well as a variety of data sources.
| Relationship classes | On-the-fly relates | Joins | |
|---|---|---|---|
Typical uses | Ensuring data integrity | Editing with low overhead | Labeling, symbology |
Scope | Geodatabase | Cross database or data source | Cross database or data source |
Framework | Geodatabase data model | Defined in map layer | Relational database/SQL |
User interface for editing | ArcMap | VBA application in ArcMap | SQL queries |
User interface for navigating | ArcMap | ArcMap | SQL queries |
Composite objects | Yes | No | No |
Referential integrity | Yes | No | No |
Messaging | Yes | No | No |
Attributes | Yes | No | No |
Relationship rules | Yes | No | No |
Cardinality | One-to-one, one-to-many, many-to-many | One-to-one, one-to-many, many-to-many | One-to-one, many-to-one |
Pros | Manages referential integrity and messaging behavior via ArcMap attributes inspector | No editing overhead, can cross workspace and data source type | No editing overhead; can cross workspace and data source type; can be used for SQL queries, labeling, and symbology |
Cons | Incurs editing overhead; must be defined only between tables in same geodatabase within the same user schema; still requires joins for SQL query, labeling, and symbology | No referential integrity; no messaging; still requires joins for SQL query, labeling, and symbology | No referential integrity, no messaging, no support for many-to-many relationships; one-to-many relationships involving feature classes not supported |