Hello, I'm trying to create a simple UNION but is not working is displaying the next message:

TITLE: Microsoft Report Designer
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An error occurred while executing the query.
Incorrect syntax near the keyword 'UNION'.

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ADDITIONAL INFORMATION:

Incorrect syntax near the keyword 'UNION'. (Microsoft SQL Server, Error: 156)

For help, click: http://go.microsoft.com/fwlink?ProdName=Microsoft+SQL+Server&ProdVer=09.00.1406&EvtSrc=MSSQLServer&EvtID=156&LinkId=20476

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BUTTONS:

OK
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And this is my UNION:

SELECT IdUsuario, Nombre
FROM Usuario
ORDER BY Nombre
UNION
SELECT Null, 'All'

How can I solve this?