第一题: SELECT class_id,AVG(score) average FROM students GROUP BY class_id; 第二题: SELECT class_id,gender, AVG(score) average FROM students GROUP BY class_id,gender;
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用户8895115920
第一题: SELECT class_id,AVG(score) average FROM students GROUP BY class_id; 第二题: SELECT class_id,gender, AVG(score) average FROM students GROUP BY class_id,gender;