To Create a Join

A join adds the properties from a data table (secondary table) to an existing Feature Class layer (primary table). The original data remains unchanged in its source—the join exists only within your map.

To create a join

1. Prepare to create a join by doing the following:
   • Ensure the primary and secondary sources share one or more common fields, for example Parcel_ID or County_Name. These fields do not have to have the same name in both sources, but they must use the same data type.
   • Simplify your secondary table data as much as possible. For example, remove unnecessary records or tables.
   • Connect to both the primary and secondary sources using one of the FDO Providers in Data Connect. When you connect to a secondary source that has no geometry data, you need not add anything to the map—you can just establish the connection and close the Data Connect window.
2. In Display Manager, right-click a feature layer Create A Join.

   The layer you right-click is the primary source.

3. In the Table (Or Feature Class) To Join To list in the Create a Join / Edit a Join dialog box, select the table or feature class whose data you will to join to the layer.

   Your selection is the secondary source. If this source contains multiple tables, choose the one to use for the join.

4. In the This Column From The Left Table list, select the join key (the common field or property) for the primary source, for example, Parcel_ID or County_Name.
5. In the Matches This Column From The Right Table list, select the matching field or property in the secondary source.
6. Under Type Of Joins, select the type of join to create:
   • Keep All Records On The Left (a left outer join)
   • Keep Only Left-Side Records With A Match (an inner join)
7. Under Relationship With Secondary Records (Cardinality), choose one of the following:
   • One-To-One matches one secondary source record to each primary source item. Any extra secondary source records are ignored.
   • One-To-Many creates a new feature for each extra record in the secondary source.
8. Click OK.

In the Data Table for the primary source (the feature layer to which you joined the data), the newly joined properties are appended to the right of the native feature data. The joined properties are gray, to indicate that they are read-only. In the column title, the name of the table you joined precedes the property name.