revDatabaseColumnIsNull
Type
function
Summary
Returns true if the specified database field has a null value, false otherwise.
Syntax
revDatabaseColumnIsNull(<recordSetID>, <columnNumber>)
Description
Use the revDatabaseColumnIsNull function to find out whether one of the 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.
The revDatabaseColumnIsNull function is part of the Database library. To ensure that the function works in a standalone application, you must include this custom library when you create your standalone. In the Inclusions pane of the Standalone Application Settings window, make sure both the "Database" library checkbox and those of the database drivers you are using are checked.
Parameters
| Name | Type | Description |
|---|---|---|
recordSetID | The number returned by the revQueryDatabase function when the record set (database cursor) was created. | |
columnNumber | The number of the column. |
Examples
revDatabaseColumnIsNull(currentResults,the number of items in myString)
repeat while revDatabaseColumnIsNull(12,3) -- is field 3 null?
Related
control structure: function
function: revDatabaseColumnNames, revDatabaseColumnLengths, revDatabaseColumnNumbered
glossary: LiveCode custom library, Standalone Application Settings, database field, record, return, standalone application
library: Database library
Compatibility and Support
Introduced
LiveCode 1.1.1
OS
mac
windows
linux
ios
android
Platforms
desktop
server
mobile