In UNION queries only ORDER BY is applied to the final recordset. All other clauses belong to particular SELECT. Your query asks for 10 records from the first select and all records from the second select.

>I have this SQL and I cannot understand why it returns 11 rows when there is a TOP 10 syntax:
>
>

>DECLARE @Enabled Bit
>DECLARE @Public Bit
>DECLARE @Public2 Bit
>
>SET @Enabled=1
>SET @Public=1
>SET @Public2=1
>
>SELECT TOP 10 Class.Title,Class.Notes,Class.AddDate,Class.ModDate,Class.Numero
> FROM Class
> UNION ALL
> SELECT ClassMethod.Title,ClassMethod.Notes,ClassMethod.AddDate,ClassMethod.ModDate,ClassMethod.Numero 
>  FROM ClassMethod
>  ORDER BY AddDate DESC
>