A.CREATE VIEW v1 AS SELECT 所在系，COUNT(*) FROM 学生表 GROUP BY 所在系

B.CREATE VIEW v1 AS SELECT 所在系，SUM(*) FROM 学生表 GROUP BY 所在系

C.CREATE VIEW v1(系名，人数) AS SELECT 所在系，SUM(*) FROM 学生表 GROUP BY 所在系

D.CREATE VIEW v1(系名，人数) AS SELECT 所在系，COUNT(*) FROM 学生表 GROUP BY 所在系