Add Field (Data Management)
Summary
Adds a new field to a table or the table of a feature class, feature layer, raster catalog, and/or rasters with attribute tables.
Usage
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Coverages, stand-alone tables, feature classes from ArcSDE and personal or file geodatabases, layer files, raster catalogs, and shapefiles will work as valid input for this command. VPF and CAD feature data overlays will not work since they are read-only formats that are not native to ArcGIS.
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For coverages, shapefiles, and dBase tables, if field type defines a character, blanks are inserted for each record. If field type defines a numeric item, zeros are inserted for each record.
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The added field will always be displayed at the end of the table.
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The Field Length parameter is only applicable on fields of type text or blob.
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For geodatabases, if field type defines a character or number <null> is inserted into each record if the Field Is Nullable parameter default is accepted.
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A shapefile does not support alias for fields, so you cannot add a field alias to a shapefile.
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It is only possible to add a field that is not nullable to an empty geodatabase feature class or table. This tool cannot add a field that is not nullable when the rows already exist.
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The Field Domain parameter can use an existing domain from a feature class in a personal, file, or SDE geodatabase. The name of an existing domain must be entered. Entering invalid domain names or values will not cause the tool to fail but it will be ignored and no domain will be set for the field.
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The precision and scale of a field describe the maximum size and precision of data that can be stored in the field. The precision describes the number of digits that can be stored in the field and the scale describes the number of decimal places for float and double fields. For example, if the field value is 54.234, then scale = 3 and precision = 5.
Use the following guidelines for choosing the correct field type for a given precision and scale:
- When you create a float, double, or integer field and specify 0 for precision and scale, the tool will attempt to create a binary type field if the underlying database supports it. Personal and file geodatabases support only binary type fields, and precision and scale are ignored.
- When you create float and double fields and specify a precision and scale, if your precision is greater than 6, use a double; otherwise, use a float. If you create a double field and specify a precision of 6 or less, a float field is created. If you create a float field and specify a precision greater than 6, a double field is created.
- If you specify a scale of 0 and a precision of 10 or less, you should be creating integer fields. When creating integer fields, your precision should be 10 or less, or your field may be created as double.
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When creating a new field in a geodatabase feature class or table, you can specify the field's type, but not its precision, and scale. Even if the dialog box allows you to add a value for precision or scale, it will be ignored during execution.
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Fields set as required are permanent and you will not be able to delete them with future processing. To allow for deletion at a later time set the field to non-required (the default).
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A field of type raster allows you to have a raster image as an attribute. It is stored within or alongside the geodatabase. This is helpful when a picture is the best way to describe a feature. Precision, scale, and length cannot be set for fields of type raster.
Syntax
| Parameter | Explanation | Data Type |
in_table |
The input table to which the specified field will be added. The field will be added to the existing input table and will not create a new output table. Fields can be added to feature classes of ArcSDE, file or personal geodatabases, coverages, shapefiles, raster catalogs, stand-alone tables, rasters with attribute tables, and/or layers. | Mosaic Layer; Raster Catalog Layer; Raster Layer; Table View |
field_name |
The name of the field that will be added to the input table. | String |
field_type |
The field type of the new field.
| String |
field_precision (Optional) |
The number of digits that can be stored in the field. All digits are counted no matter what side of the decimal they are on. If the input table is a personal or file geodatabase the field precision value will be ignored. | Long |
field_scale (Optional) |
The number of decimal places stored in a field. This parameter is only used in float and double data field types. If the input table is a personal or file geodatabase the field scale value will be ignored. | Long |
field_length (Optional) |
The length of the field being added. This sets the maximum number of allowable characters for each record of the field. This option is only applicable on fields of type text or blob. | Long |
field_alias (Optional) |
The alternate name given to the field name. This name is used to give more descriptive names to cryptic field names. The field alias parameter only applies to geodatabases and coverages. | String |
field_is_nullable (Optional) |
Specifies whether the field can contain null values. Null values are different from zero or empty fields and are only supported for fields in a geodatabase.
| Boolean |
field_is_required (Optional) |
Specifies whether the field being created is a required field for the table; only supported for fields in a geodatabase.
| Boolean |
field_domain (Optional) |
Used to constrain the values allowed in any particular attribute for a table, feature class, or subtype in a geodatabase. You must specify the name of an existing domain for it to be applied to the field. | String |
Code Sample
The following Python window script demonstrates how to use the AddField tool in immediate mode.
import arcpy
from arcpy import env
env.workspace = "C:/data/airport.gdb"
arcpy.AddField_management("schools", "ref_ID", "LONG", 9, "", "", "refcode", "NULLABLE", "REQUIRED")
The following stand-alone script demonstrates how to use the AddField tool.
# Name: AddField_Example2.py
# Description: Add a pair of new fields to a table
# Import system modules
import arcpy
from arcpy import env
# Set environment settings
env.workspace = "C:/data/airport.gdb"
# Set local variables
inFeatures = "schools"
fieldName1 = "ref_ID"
fieldPrecision = 9
fieldAlias = "refcode"
fieldName2 = "status"
fieldLength = 10
# Execute AddField twice for two new fields
arcpy.AddField_management(inFeatures, fieldName1, "LONG", fieldPrecision, "", "",
fieldAlias, "NULLABLE")
arcpy.AddField_management(inFeatures, fieldName2, "TEXT", "", "", fieldLength)