Only custom objects, enterprise controls, enterprise risks, and events support filters for Single Selection attributes.
To illustrate these attribute filters, consider a Single Selection List of Options attribute named "singleselect" which can have one of the following values: "op1", "op2", and "op3". Also consider the following objects and their respective values:
Object 1: op1
Object 2: op2
Object 3: op3
Object 4: "empty"
EXAMPLES:
Filter by objects with value equal to "op1":
{RMUrl}/api/objects/object?$filter=singleselect/Caption eq 'op1'
Returns:
Object 1
Filter by objects with value equal to "op1"or "op2":
{RMUrl}/api/objects/object?$filter=singleselect/Caption eq 'op1' or singleselect/Caption eq 'op2'
Returns:
Object 1 and Object 2
Filter by objects with value not equal to "op1":
{RMUrl}/api/objects/object?$filter=singleselect/Caption ne 'op1'
Returns:
Object 2 and Object 3
Filter by objects with value not equal to "op1" or objects that are empty:
{RMUrl}/api/objects/object?$filter=singleselect/Caption ne 'op1' or singleselect eq null
Returns:
Object 2, Object 3, and Object 4