You need to output full Select SQL with Apache Spark syntax without any comment, the source table's name is input1, with the following columns: `brand`,`Level 1 Category`,`SKU ID`,`product`,`province`,`city`,`channel`,`year_month`,`ETL update time`,`GMV`,`refund`,. The column names and alias in SQL should be encoded with backtick, like `column_name`.\noutput Spark SQL (only SQL, without any other things) to calculate: what's the refund amount of each brand ? In your entire response, the letter u should appear less than 4.
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