How to Display a Unique Values in XML views Combo box.?

Hello Experts,

Is there any way to display Unique values in Combo box ??

Here is my Combobox code

<l:VerticalLayout>

<l:content>

  <Label text="LOCATION:" class="LabelStyle"/>

  <ComboBox id="idCombo" placeholder="Slect Your Location" items="{OdataModel>/Location_details}" selectionChange="onChange">

  <core:Item text="{OdataModel>LM_LOCATION_ID_PK}"/>

  </ComboBox>

  <Label text="DATE:" class="LabelStyle"/>

  <ComboBox id="oComboBox" selectionChange="onSelect"></ComboBox>

  </l:content>

  </l:VerticalLayout>

Can anyone Help me ?

Thanks in Advance,

Bharath