NullAllowed (Property)

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How to know whether a data file supports the management of NULL value?

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How to know whether a data file supports the management of NULL value?
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See also

NullAllowed (Property)

In french: NullAutorisé

Available only with these kinds of connection

The Property NullAuthorized allows to manage the NULL value in the fields of the HFSQL data files.

This property is used to:

Find out the management mode of the NULL value for an item of a data file described in the data model editor.
Define the management mode of the NULL value when an item of a data file is described by programming.

If a data file supports the NULL value and if its item allows the management of NULL, you will have the ability to use Null to assign NULL to the item for the current record for example.

The Property NullAuthorized is useful for example to not allow the NULL value for some fields in the programmatically defined a data file (this file supports the NULL value).

Remark: From version 19, HFSQL is the new name of HyperFileSQL.

Syntax

Finding out whether the item allows the management of the NULL value Hide the details

Result> = <Data file>.<Item>.NullAllowed

<Result>: Boolean

True if the item allows the management of the NULL value,
False if the item does not support the management of the NULL value.

<Data file>: Character string (with or without quotes)

Logical name of the data file used. This name was defined in the data model editor or by the File description type.

<Item>: Character string (with or without quotes)

Name of the item used. This name was defined in the data model editor or by the Item description type.

Defining the management mode of the NULL value for the item Hide the details

Item>.NullAllowed = <Management mode

<Item>: Character string (with or without quotes)

Name of the item used. This name was defined by the Item description type.

<Management mode>: Boolean

True to manage the NULL value,
False not to support the NULL value.

Remarks

How to know whether a data file supports the management of NULL value?

To know if a data file allows or not the handling of the NULL value, use the Property NullSupported.

Caution:

The assignment of the Property NullAllowed on a data file or a field that does not support the management of the NULL value is forbidden: a fatal error occurs.
The Property NullAllowed query on a data file or a field that does not support NULL value handling always returns False.

Limits

The NULL value cannot be used:

on the array items.
on the automatic identifiers.
on the composite keys.