Name: revDatabaseColumnIsNull

Type: function

Syntax: revDatabaseColumnIsNull(<recordSetID>, <columnNumber>)

Summary: <return|Returns> true if the specified <database field> has a null value, false otherwise.

Synonyms: revdb_columnisnull

Introduced: 1.1.1

OS: mac,windows,linux,ios,android

Platforms: desktop,server,web,mobile

Security: disk,network

Example:
revDatabaseColumnIsNull(currentResults,the number of items in myString)

Example:
repeat while revDatabaseColumnIsNull(12,3) -- is field 3 null?

Parameters:
recordSetID: The number returned by the revQueryDatabase function when the record set (database cursor) was created.
columnNumber: The number of the column.

Returns (bool): The <revDatabaseColumnIsNull> function returns true or false.

Description:
Use the <revDatabaseColumnIsNull> <function> to find out whether one of the <database field|database fields> in the current <record> is set to a value.

A null value in a SQL database refers to a value that is unknown or not applicable. For example, if the price of an item in a product database has not yet been determined, its "Price" field is typically set to null. The null value is not zero: the item's price is not zero, but undetermined.

The special null value allows the database to differentiate between an unknown value deliberately inserted, and a value of zero or a blank field. 

This means that if the data value of the database field is empty or zero, the <revDatabaseColumnIsNull> <function> returns false. It only returns true if the field's value is not set at all.

>*Important:*  The <revDatabaseColumnIsNull> <function> is part of the <Database library>. To ensure that the <function> works in a <standalone application>, you must include this <Revolution custom library|custom library> when you create your <standalone application|standalone>. In the Inclusions section of the General screen of the <Standalone Application Settings> window, make sure the "Database Support" checkbox is checked and the database drivers you are using are selected in the list of database drivers.

Changes:
The revDatabaseColumnIsNull synonym was added in version 2.0.

References: function (control_st), revDatabaseColumnNames (function), revDatabaseColumnLengths (function), revDatabaseColumnNumbered (function), Database library (library), Revolution custom library (library), Standalone Application Settings (glossary), database field (glossary), record (glossary), return (glossary), standalone application (glossary)

Tags: database
