Joining attributes in one table to another

Typically, you'll join a table of data to a layer based on the value of a field that can be found in both tables. The name of the field does not have to be the same, but the data type has to be the same; you join numbers to numbers, strings to strings, and so on. You can perform a join with either the Join Data dialog box, accessed by right-clicking a layer in ArcMap, or the Add Join tool.

Field properties, such as aliases, visibility, and number formatting, are maintained when a join is added or removed.

When joining tables, the default option is to keep all records. If a record in the target table doesn't have a match in the join table, that record is given null values for all the fields being appended into the target table from the join table.

With the keep only matching records option, if a record in the target table doesn't have a match in the join table, that record is removed from the resultant target table. If the target table is the attribute table of a layer, features that don't have data joined to them are not shown on the map.

Steps:

1. In the table of contents, right-click the layer or table you want to join, point to Joins and Relates, then click Join.

   You can also click the Table Options button on an open table window to access the Join Data dialog box.

   Tip:

   If you do not want your fields to be prefixed with the table name after a join, open the attribute table, click the Table Options menu, then uncheck Show Field Aliases.

2. Click the What do you want to join to this layer? arrow and click Join attributes from a table.
3. Click the field on which the join will be based.
4. Choose the table to join to the layer or table. If it is not currently part of the map, click the browse button to search for it on disk.
5. Click the field in that table on which the join will be based.
6. Choose whether to keep all records or only matching records.
7. Click OK.

Tip:

If you want to permanently save joined data with your geographic features, export the data to a new feature class, right-click the layer in the table of contents, point to Data, then click Export data.

Tip:

When editing joined data, you cannot directly edit the joined columns. To edit the joined data, you must first add the joined tables or layers to ArcMap. You can then perform edits on this data separately. These changes are reflected in the joined columns.