1. 使用GROUP BY子句创建分组 示例: SELECT vend_id, COUNT ( * ) AS num_prods FROM Products GROUP BY vend_id; 1. 使用GROUP BY子句创建分组 示例: SELECT vend_id, COUNT(*) AS num_prods FROM Products GROUP BY vend_id; ，网站空间，香港空间，网站空间
