Special elements of tables

There are several concepts for working with tables and attributes that make it easier to perform analysis, understand the relationships between your data, and edit your attribute information. These special elements of tables are briefly discussed in this help topic.

Joins and relates

Most database design guidelines promote organizing your database into multiple tables—each focused on a specific topic—instead of one large table containing all the necessary fields. Having multiple tables prevents duplicating information in the database because you store the information only once in one table. When you need information that isn't in the current table, you can link the two tables together.

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.

When the layers on your map don't share a common attribute field, you can join them using a spatial join, which joins the attributes of two layers based on the location of the features in the layers.

Learn more about joins and relates

Domains and subtypes

A database is only as good as the information it contains. Over time, you'll need to edit the information in your database to keep it accurate and up-to-date. ArcMap lets you edit the attributes of features displayed on your map and also the attributes contained in tables that are not represented geographically on the map (for example, a table of monthly sales figures).

Attribute domains are rules that indicate valid values for a field. They enforce data integrity by restricting what data values a user can add to a particular field.

Subtypes are classifications within a feature class or table. They allow you to logically group features based on a unique characteristic or behavior of the data. This characteristic or behavior is represented by the values of one field in the table. For example, for a table of hydrology, you could have subtypes for different types of waterways, such as creeks, streams, channels, canals, and rivers. For each of these subtypes, you could apply different topology rules, connectivity rules, default values, and relationship rules.

Learn more about domains and subtypes

Attribute indexes

Attribute indexes can speed up attribute queries on feature classes and tables. An attribute index is an alternate path used by ArcGIS to retrieve a record from a table. For most types of attribute queries, it is faster to look up a record with an index than to start at the first record and search through the entire table.

You can create an attribute index in ArcCatalog or with geoprocessing tools.

Learn more about attribute indexes

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