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- How to know whether a data file supports the management of NULL value?
- Limitations
Null (Property)
  No disponible con estos tipos de conexión
The Null property is used to manage the NULL value in items of HFSQL data files or in items of data files accessed via Native Connectors. This property is used to: - Assign NULL to the item for the current record.
- Find out whether the item is associated with the NULL value for the current record.
- Define the default value of an item when the item is described programmatically. You can also use the DefaultValue property.
 Management of nullable values If the "Permitir tipos que admiten valores NULL" option is checked in the project description, this property is no longer needed to find out or modify the value of the field. This option allows you to: - directly assign a Null value to an HFSQL item using the following syntax:
- check whether an HFSQL item holds a Null value using the following syntax:
IF File.Item = Null THEN
...
END
For more details, see NULL value management: Allow nullable types.
Customer.CellPhone.Null = True
Sintaxis
Check whether the item is associated with the NULL value Ocultar los detalles
<Result> = <Data file>.<Item>.Null
<Result>: Boolean - True if the item associated with the current record has a NULL value,
- False otherwise.
<Data file>: Character string Logical name of the data file used. This name was defined in the data model editor or with the File Description type. <Item>: Character string Name of the item used. Observaciones How to know whether a data file supports the management of NULL value? - To determine if a data file allows the use of the NULL value, use the NullSupported property.
- To determine if am item allows the use of the NULL value, use the NullAllowed property.
Caution: - Assigning the property Null property on a data file or field that does not support NULL value management is prohibited: a fatal error is displayed.
- Reading the Null property on a data file or item that does not support the NULL value always returns False.
Limitations - The NULL value cannot be used:
- on array items.
- on automatic identifiers.
- on composite keys.
- The NULL value cannot be assigned several times to an item that takes the management of duplicates into account.
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