You define the properties of a table or feature class when you create it in a database or geodatabase. You can create a table or feature class by right-clicking a database connection (or feature dataset in a geodatabase), pointing to New, and clicking either Feature Class or Table. This opens the Create Feature Class wizard or the Create Table wizard.
The properties you define when creating data are shown in the following table. The check marks indicate to which object—a table or a feature class (spatial tables)—a property applies.
| Property | Table | Feature class |
|---|---|---|
Name and alias |
Aliases can be set only in geodatabases. |
Aliases can be set only in geodatabases. |
Geometry type |
| |
Spatial type |
Databases only. | |
Geometry properties, including the following:
|
X,y tolerance is set only in geodatabases. | |
Geodatabases only. |
Geodatabases only. | |
Field name, data type, and length |
|
|
Names, aliases, feature types, and spatial properties are discussed in the sections below. For information on the other properties, follow the links in the table.
Table and feature class names
When you create a table or a feature class (which is a table with a spatial column and hereafter referred to as a table), give it a name that indicates what data it stores. Table names must be unique in a geodatabase—you can't have more than one table with the same name.
ArcGIS uses fully qualified table names to accommodate possible duplicate names. A fully qualified table name includes the name of the schema where the table is stored. In some of the database management systems that ArcGIS supports, the name of the database or the data source name is also part of the fully qualified table name. As long as one of the components in the fully qualified name is unique, the table name is considered unique.
Tip:
It is recommended that you do not reuse table names even if the tables are stored in different schemas. Table names should communicate the contents of the table. If you have two tables with the same content, rather than two different tables in separate schemas, create a single table and grant other users access to it. Conversely, if the data is distinctly different, name the tables accordingly. For example, if you have two tables—one that stores alpaca ranges and the other that stores the location of alpaca farms—don't create two tables named alpacas. Instead, create one table named alpaca_ranges and one named alpaca_farms.
For more information, see Define feature class properties and review the table that summarizes feature class and table name rules and limitations.
Aliases
When you create a table or feature class in a geodatabase, you can assign an alias to it. An alias is an alternate name. When you assign an alias to a table or feature class, that is the name users see when they add it to the map. Users can look up the name of the table or feature class on the Source tab on the Layer Properties dialog box.
When you create a feature class or table in a geodatabase using geoprocessing tools, there is no parameter to specify the alias. You can set an alias for the feature class or table on the Source tab of the Properties dialog box. Right-click the feature class or table in the Catalog pane, click Properties, click the Source tab, and click the Alias property to enable editing of the name. Type an alias name and click OK to set an alias for that feature class or table.
Fields
A table is a collection of records (rows) and fields (columns) that is used to organize information about a single topic or object. When you create a table or add fields to an existing table, you define the data type used to store the data in each field. For example, if you have a SURNAME field in a table of customers, the field is a text data type that stores customers' last names.
In addition, you can rename fields in a table or feature class in the fields view.
To learn more about field names, renaming fields, or field name rules and limitations, see Define fields in tables.
Feature types
Feature types are only defined for feature classes and are defined at the time of feature class creation. They specify which type of geometry will be stored in the feature class.
Choose a feature type that best represents the real-world object you are trying to symbolize on your maps. This may vary depending on the map scale with which you use the feature class. Also consider the type of analyses you may want to perform with the data.
The following table contains a list of the types of features you can specify for a feature class, along with descriptions of typical objects or concepts represented with that feature type. A third column contains notes on the type of analyses or relationships you can create or perform with only this feature type.
| Feature type | Real-world object or concept | Unique spatial analyses or relationships |
|---|---|---|
Polygons | Objects or places that have area, such as water bodies, jurisdictional or service area boundaries, wildlife ranges, or flood zones |
|
Lines | Linear objects, such as rivers, streets and highways, utility lines, or survey transects |
|
Points | A narrowly localized position or spot, such as a survey marker, sample point, telephone pole, or individual plant |
|
Multipoints (Geodatabase feature classes only) | An object or place that is composed of multiple localized positions having the same attributes, for instance, a stand of the same species of tree, an island chain, multiple buildings in the same office complex, or lidar or sonar point clusters | |
Multipatches (Geodatabase feature classes only) | Three-dimensional features, such as buildings, mountains, water tables, and planets |
|
Annotation (Geodatabase feature classes only) | Place or object names or identifiers, such as street names, hydrant ID numbers, land values, or elevation |
|
Dimensions (Geodatabase feature classes only) | Measurements, such as distances, lengths, widths, and depths |
|
You may need to have feature classes of different feature types represent the same data. For example, if you usually create maps at a scale at which it makes sense to use a polygon feature class to represent city parks (approximately 1:25,000 to 1:100,000) but you sometimes need to create maps at a scale at which you need the parks to be shown as points (approximately 1:250,000 to 1:500,000), you can create a second parks feature class that uses centroid points to represent the location of the parks.
Or you may need data represented in one feature type (for mapping purposes), but you need the same data represented in a different feature type to perform certain analyses. For example, you have a river feature class that stores the rivers as lines. This works fine for modeling flow or analyzing where rivers cross other features, but to perform any sort of area analysis, such as clipping or calculating the area of your soils polygon feature class that is covered by rivers, you also must model your rivers as polygon features so they have area and not just length.
Spatial properties
Tables that store spatial data, such as those that make up feature classes, have properties that define where the data is located in space:
- X,y coordinates—The data's location in two-dimensional space.
- Z-coordinates—The data's location in the third dimension.
- M-coordinates—Measures that can be used to calculate distances along line features.
For an explanation of x-, y-, z-, and m-coordinates, see Feature class basics.
- Spatial reference—Includes a coordinate system; x-, y-, z-, and m-tolerance values and x-, y-, z-, and m-resolution.
For details on spatial references, see The properties of a spatial reference.
Together, these properties allow you to find the location of a given feature on the earth.