SELECT * FROM test_user GROUP BY user_id -- 正常
SELECT * FROM test_user GROUP BY birthday -- 报错
SELECT * FROM test_user GROUP BY age -- 报错
user_id是自增主键
SELECT * FROM test_user GROUP BY user_id -- 正常
SELECT * FROM test_user GROUP BY birthday -- 报错
SELECT * FROM test_user GROUP BY age -- 报错
user_id是自增主键