CREATE TABLE table_204_220 (id DECIMAL, "entered" TEXT, "weeks in\ top 10" DECIMAL, "single" TEXT, "artist" TEXT, "peak" DECIMAL, "peak\ reached" TEXT, "weeks\ at peak" DECIMAL)

which single was the last one to be on the charts in 1993 ?
SELECT "single" FROM table_204_220 WHERE "entered" = 1993 ORDER BY "entered" DESC LIMIT 1
SELECT "single" FROM "table_204_220" WHERE "entered" = 1993 ORDER BY "entered" DESC NULLS LAST LIMIT 1