Question: Who was the leader at the summit earlier than 1956, when Carcassonne shows for finish?
SQL: SELECT "Leader at the summit" FROM "2-18404734-1" WHERE "Year" < 1956.0 AND "Finish" = 'Carcassonne';

Question: What year was finish Toulouse, and stage was larger than 12?
SQL: SELECT SUM("Year") FROM "2-18404734-1" WHERE "Finish" = 'Toulouse' AND "Stage" > 12.0;

Question: What is the highest stage number for a year later than 1948, leader at the summit was Group, and finish was Bagnères-de-Bigorre?
SQL: SELECT MAX("Stage") FROM "2-18404734-1" WHERE "Year" > 1948.0 AND "Leader at the summit" = 'Group' AND "Finish" = 'Bagnères-de-Bigorre';