Labeling Expression Where: is not null

[DavinShokes1]

The REST API shows the following example to query:

"where" : "NAME LIKE 'A%'"

I'm trying to only label features with values.

I've tried to update the definition of the service and the specific feature layer with: "where" : "NAME is not null" . But the labels disappear completely.

I've also tried to use the the example esri provides: "where" : "NAME LIKE 'A%'"

However, something happens in the background to encode the value: "where":"NAME LIKE \u0027A%\u0027"

How do I set labelingInfo where:"Field is not null" ?