CREATE TABLE table_501 ("Season" CLOB, "Competition" CLOB, "Round" CLOB, "Club" CLOB, "1st leg" CLOB, "2nd leg" CLOB, "Aggregate" CLOB)

What is the 1st leg when 2nd leg is 1 0 and competition is uefa champions league?
SELECT "1st leg" FROM table_501 WHERE "2nd leg" = '1–0' AND "Competition" = 'UEFA Champions League'
SELECT "1st leg" FROM "table_501" WHERE "2nd leg" = '1–0' AND "Competition" = 'UEFA Champions League'