CREATE TABLE table_30171 ("Round" CLOB, "Main date" CLOB, "Number of fixtures" FLOAT, "Clubs" CLOB, "New entries this round" CLOB, "Prize money" CLOB, "Player of the Round" CLOB)

What is the main date when the round is third round qualifying?
SELECT "Main date" FROM table_30171 WHERE "Round" = 'Third Round Qualifying'
SELECT "Main date" FROM "table_30171" WHERE "Round" = 'Third Round Qualifying'