Deciding between relationship classes, joins, and relates
This topic applies to ArcEditor and ArcInfo only.
Note:Although relationship classes can be both created and edited in ArcInfo and ArcEditor, they are read-only in ArcView. The feature classes participating in the relationship class will also be read-only in ArcView.
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 Edited 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; still requires joins for SQL query, labeling, and symbology |
No referential integrity; no messaging; no support for many-to-many cardinality; 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 |