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  • How to know whether a data file supports the management of NULL value?
  • Limitations
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Stored procedures
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.
Versions 17 and later
iPhone/iPad This property is now available for iPhone/iPad applications.
New in version 17
iPhone/iPad This property is now available for iPhone/iPad applications.
iPhone/iPad This property is now available for iPhone/iPad applications.
Versions 18 and later
Universal Windows 10 App This property is now available in Windows Store apps mode.
New in version 18
Universal Windows 10 App This property is now available in Windows Store apps mode.
Universal Windows 10 App This property is now available in Windows Store apps mode.
Remark: From version 19, HFSQL is the new name of HyperFileSQL.
Versions 21 and later
Universal Windows 10 App This property is now available in Universal Windows 10 App mode.
New in version 21
Universal Windows 10 App This property is now available in Universal Windows 10 App mode.
Universal Windows 10 App This property is now available in Universal Windows 10 App mode.
Example
// 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.
WINDEVWEBDEV - Server codeReports and QueriesUniversal Windows 10 AppiPhone/iPadIOS WidgetUser code (UMC)Ajax

Assigning NULL to an item Hide the details

<Data file>.<Item>.Null = <Null value>
<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 item used.
<Null value>: Boolean
  • True to assign NULL to the specified item for the current record.
  • False otherwise.
WINDEVWEBDEV - Server codeReports and QueriesUniversal Windows 10 AppiPhone/iPadIOS WidgetUser code (UMC)Ajax

Defining the default value of an item in a file defined through programming Hide the details

<Data file>.<Item>.Null = <Null value>
<Data file>: Character string
Logical name of the data file used. This name was defined by the File Description type.
<Item>: Character string
Name of item used.
<Null value>: Boolean
  • True if the default value of item must be null,
  • False otherwise.
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.
  • Versions 16 and later
    To determine if am item allows the use of the NULL value, use the NullAllowed property.
    New in version 16
    To determine if am item allows the use of the NULL value, use the NullAllowed 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.
Minimum version required
  • Version 9
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