check query range value: null or specific value (for enum)

Hello,

I have enum value in query (one of the datasource is view, and the field may contain null value or specific value).

How can I check out for querybuildRange, whether the enum is empty or has a specific value?

i.e:

enum value is empty or enum value = 8

QueryBuildRange qbr = 

qbr = this.query().dataSourceNo(1).addRange(fieldNum(MyView, MyField));

qbr.value("null, 8"); // what shall I put here?

Thanks :)