CREATE TABLE table_78351 ("Outcome" CLOB, "Date" CLOB, "Tournament" CLOB, "Surface" CLOB, "Opponent" CLOB, "Score" CLOB)

What tournament was held on 21 May 2006?
SELECT "Tournament" FROM table_78351 WHERE "Date" = '21 may 2006'
SELECT "Tournament" FROM "table_78351" WHERE "Date" = '21 may 2006'