CREATE TABLE "jersey_progress" (
  "stage" real,
  "winner" text,
  "general_classification" text,
  "points_classification" text,
  "mountains_classification" text,
  "combination_classification" text,
  "team_classification" text
);

Question: How many combination classifications have the winner as Erik Zabel and a points classification as Alessandro Petacchi
SQL: SELECT COUNT("combination_classification") FROM "jersey_progress" WHERE "points_classification"='Alessandro Petacchi' AND "winner"='Erik Zabel';

Question: If winner is alejandro Valverde and the points Classification is by Erik Zabel, who is the mountain classification?
SQL: SELECT "mountains_classification" FROM "jersey_progress" WHERE "winner"='Alejandro Valverde' AND "points_classification"='Erik Zabel';

Question: How many teams have a combination classification of Alejandro Valverde and a Points classification of Alessandro Petacchi?
SQL: SELECT COUNT("team_classification") FROM "jersey_progress" WHERE "combination_classification"='Alejandro Valverde' AND "points_classification"='Alessandro Petacchi';