isnull()

Evaluates its sole argument and returns a bool value indicating if the argument evaluates to a null value.

isnull(parse_json("")) == true

Syntax

isnull(Expr)

Returns

True or false, depending on whether or not the value is null.

Notes

  • string values cannot be null. Use isempty to determine if a value of type string is empty or not.
x isnull(x)
"" false
"x" false
parse_json("") true
parse_json("[]") false
parse_json("{}") false

Example

T | where isnull(PossiblyNull) | count