CREATE TABLE table_16189 ("Team" CLOB, "Outgoing manager" CLOB, "Manner of departure" CLOB, "Date of vacancy" CLOB, "Replaced by" CLOB, "Date of appointment" CLOB, "Position in table" CLOB)

What is the date of appointment when the date of vacancy is 21 december 2007?
SELECT "Date of appointment" FROM table_16189 WHERE "Date of vacancy" = '21 December 2007'
SELECT "Date of appointment" FROM "table_16189" WHERE "Date of vacancy" = '21 December 2007'