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  • How to know whether a data file supports the management of NULL value?
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Stored procedures
..Null is used to manage the NULL value in the items of HFSQL data files or in the items of data files accessed by 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 by programming.
Versions 17 and later
iPhone/iPad This property is now available for the iPhone/iPad applications.
New in version 17
iPhone/iPad This property is now available for the iPhone/iPad applications.
iPhone/iPad This property is now available for the 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> = <File Name>.<Item Name>..Null
<Result>: Boolean
  • True if the item associated with the current record has a NULL value,
  • False otherwise.
<File name>: Character string (with or without quotes)
Logical name of data file used. This name was defined in the data model editor or by the File description type.
<Item name>: Character string (with or without quotes)
Name of item used.
WINDEVWEBDEV - Server codeReports and QueriesiPhone/iPadWindows MobileUniversal Windows 10 AppAjaxUser code (UMC)

Assigning NULL to an item Hide the details

<File name>.<Item name>..Null = <Null value>
<File name>: Character string (with or without quotes)
Logical name of data file used. This name was defined in the data model editor or by the File description type.
<Item name>: Character string (with or without quotes)
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 QueriesiPhone/iPadWindows MobileUniversal Windows 10 AppAjaxUser code (UMC)

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

<File name>.<Item name>..Null = <Null value>
<File name>: Character string (with or without quotes)
Logical name of data file used. This name was defined by the File description type.
<Item name>: Character string (with or without quotes)
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 find out whether a data file allows (or not) the management of NULL value, use ..NullSupported.
  • Versions 16 and later
    To find out whether an item allows (or not) the management of NULL value, use ..NullAllowed.
    New in version 16
    To find out whether an item allows (or not) the management of NULL value, use ..NullAllowed.
    To find out whether an item allows (or not) the management of NULL value, use ..NullAllowed.
Caution:
  • ..Null cannot be assigned to a data file or an item that does not support the management of NULL value: a fatal error occurs.
  • Using ..Null on a data file or item that does not support the management of NULL value always returns False.

Limits

  • 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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