Null is the special value indicating that no value was entered in the input field or no value extracted via lookup, for example, when related record was not found. Null does not compare to anything including null, the result of comparison to null is always false; arithmetical and logical operations on null return null as well as most functions. To check whether the value is null, use IsNull() function. Nz(), Min(), Max() and List() functions provide special treatment for null arguments.
IsNull function, as it follows from the function name, is used to check whether a field contains any data, and returns only true or false values.
Since the IsNull function returns true or false results, it can be broadly used to set conditions in the condition functions. For example, the If(IsNull([Company Name], ToUser(“Sam Powter”)) formula, may be used for the Lead Owner column to assign all leads where the company name is undefined to a specific user – Sam Powter.
The IsNull function can revert its meaning if you use “not” before the function name. For example, the If (not IsNull([Project Manager]), “Assigned”) formula used for the Project Status column has the following meaning: if the Project Manager field in the project record is not empty, then the project status is changed to “Assigned”.
If you want to perform some operations with the field value, but are unsure whether the field is empty or not, use the Nz function: if the verified field is empty, this function returns its second argumen. In this way you may get round some difficulties with simple arithmetical operations and others. The function is applicable to various field types.
Like Sum() function List() function ignores null arguments and concatenates remaining values.
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