null, NULL, Null,

Null simply means that a value for something has not been determined.

It is not a value itself - it is a state, the state of not knowing.

An attribute can be null, as can an FME parameter. In both cases, it means that “we don’t know, yet, what value this has.” Any data type can be null, including numeric, string, Boolean, and so forth.

Null is not same thing as missing or empty.

Missing implies that we know the state of something - it should have a value, but it doesn’t.

Empty implies that we know that it does not have a value.

See also: Much Ado About Null! , More Ado About Nothing

Usage:

Null is written in a variety of ways, depending on where and how it is referenced. FME uses this convention:

<null>

It is most commonly used in reference to attribute and trait values, but also appears in text editors, conditional values, test conditions, and expressions to set null values.

Other text strings such as IFMEText geometry, datasets, and feature type names do not use this convention or store null values.

How to talk about null

These are our basic rules for null in text:

  • DO use upper case NULL in code snippets, SQL statements, or when referring to a NULL pointer.

  • DO use title case Null when referring to a GUI parameter name or choice, such as the test operator Attribute Is Null.

  • DO use lower case null in body text, unless it's at the beginning of a sentence.

  • DO NOT use "null string" - DO use "empty string.”

More Types of Nothing

  • Geometry: IFMENull is a type of FME geometry, where a feature intentionally has zero points and therefore no geometry.

  • NaN (Not a Number): A numeric value that is undefined or unrepresentable, such as division by zero or the square root of a negative number.

  • Out of bounds: A numeric value that exceeds the limits of the assigned data type, such as an integer greater than 255 for an 8-bit integer. FME returns null in this case.

  • Nodata: In raster data, an arbitrary value that represents pixels having no value associated with them.

  • NULL Reader/Writer: FME’s NULL format reader and writer read (or write) nothing, and are generally used for testing purposes.