IsNull - script and chart function

The IsNull function tests if the value of an expression is NULL and if so, returns -1 (True), otherwise 0 (False).

Syntax:

IsNull(expr )

A string with length zero is not considered as a NULL and will cause IsNull to return False.

Example: Data load script

In this example, an inline table with four rows is loaded, where the first three lines contain either nothing, - or 'NULL' in the Value column. We convert these values to true NULL value representations with the middle preceding LOAD using the Null function.

The first preceding LOAD adds a field checking if the value is NULL,using the IsNull function.

NullsDetectedAndConverted: LOAD *, If(IsNull(ValueNullConv), 'T', 'F') as IsItNull; LOAD *, If(len(trim(Value))= 0 or Value='NULL' or Value='-', Null(), Value ) as ValueNullConv; LOAD * Inline [ID, Value 0, 1,NULL 2,- 3,Value];

This is the resulting table. In the ValueNullConv column, the NULL values are represented by -.

ID	Value	ValueNullConv	IsItNull
0		-	T
1	NULL	-	T
2	-	-	T
3	Value	Value	F

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