CREATE TABLE table_77923 ("Outcome" CLOB, "Date" CLOB, "Tournament" CLOB, "Surface" CLOB, "Partner" CLOB, "Opponents in the final" CLOB, "Score" CLOB)

Who played on a hard surface?
SELECT "Partner" FROM table_77923 WHERE "Surface" = 'hard'
SELECT "Partner" FROM "table_77923" WHERE "Surface" = 'hard'