CREATE TABLE table_69731 ("Outcome" TEXT, "Date" TEXT, "Surface" TEXT, "Partner" TEXT, "Opponents" TEXT, "Score" TEXT)

What was the Surface for the Partner of J rgen Melzer, and a Date of July 16, 2011?
SELECT "Surface" FROM table_69731 WHERE "Partner" = 'jürgen melzer' AND "Date" = 'july 16, 2011'
SELECT "Surface" FROM "table_69731" WHERE "Date" = 'july 16, 2011' AND "Partner" = 'jürgen melzer'