<Tr> <Th_colspan="2"> Clay Aiken singles chronology </Th> </Tr> <Tr> <Td_colspan="2"> <Table> <Tr> <Td> "Have Yourself a Merry Little Christmas" (2005) </Td> <Td> "Mary, Did You Know?" (2005) </Td> <Td> "Without You" (2006) </Td> </Tr> </Table> </Td> </Tr> <Table> <Tr> <Td> "Have Yourself a Merry Little Christmas" (2005) </Td> <Td> "Mary, Did You Know?" (2005) </Td> <Td> "Without You" (2006) </Td> </Tr> </Table> <Tr> <Td> "Have Yourself a Merry Little Christmas" (2005) </Td> <Td> "Mary, Did You Know?" (2005) </Td> <Td> "Without You" (2006) </Td> </Tr>

Who sings christmas song mary did you know