Changing permission according to a query

[eyalseg]

I would like to change every permission of items that are created by specific user.

When making the WF with the query:

<Query>
<Lists>
<List ID="..." />
</Lists>
<ViewFields>
<FieldRef Name="ID" />
</ViewFields>
<Where>
<Eq>
<FieldRef Name="Author" LookupId="TRUE" />
<Value Type="User">USERNAME</Value>
</Eq>
</Where>
</Query>

I get empty string.

What could be the problem?

[emha]

If you want to make search by user (display) name you have to configure LookupId="FALSE".

But note search by user display name need not be unique.

To make it working with LookupId="TRUE" you have to supply user ID in place of USERNAME value