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 through programming.
// Assign NULL to the Customer.CellPhone item
Customer.CellPhone.Null = True
Syntax
Finding out whether the item is associated with the NULL value Hide the details
<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.
Remarks
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:
- It is not possible to assign a value to the Null property on a data file or item that does not support the NULL value: a fatal error occurs.
- 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 the array items.
- on the automatic identifiers.
- on the composite keys.
- The NULL value cannot be assigned several times to an item that takes the management of duplicates into account.