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