Michael Berrer คู่ต่อสู้อยู่บนพื้นผิวใด?ไม่จำเป็นต้องใช้โต๊ะทั้งหมด
On what surface was the opponent Michael Berrer?It is not neccessary to use all the tables.
 table_name_15:  (surface [ VARCHAR ] opponent [ VARCHAR) ]
SELECT surface FROM table_name_15 WHERE opponent = "michael berrer"