CAML Query Syntax

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SharePoint

Hi all,

My question is related CAML Query syntax.

This is my simple CAML query refencing fieldname to the parameter

<Where>
<Contains>
<FieldRef Name="Title"/><Value Type="Text">%firstname%</Value>
</Contains>
</Where>

Is there a way to apply conditions on %firstname% prameters.
I want to added other condition like parameter %firstname% is empty ("").

Any help appreciated..