Arithmetic operator that means "not equal to" and is used in queries.
<FieldRef Name = "Field_Name"/>
<Value Type = "Field_Type"/>
FieldRef, Value, XML
And, Or, Where
The following example queries the Status field for cases where the value does not equal Completed or is null, returning the results according to a descending sort on the Modified field. The Where element contains an Or element to group the filters.
<FieldRef Name="Modified" Ascending="FALSE"></FieldRef>