mysql - 使用“分组依据”求和

我有这个查询..

SELECT DATE_FORMAT(utcdt,GET_FORMAT(DATE,'ISO')) as utcdt,
                HOUR(utcdt) as hour,
                country,
                sum(impressions) as impressions
                FROM rtb_impressions where campaign_id='cid2204184260'
                GROUP BY utcdt, hour, country

这些是结果.....

{'impressions': Decimal('1'), 'country': 'US', 'hour': 10L, 'utcdt': '2012-10-01'}
{'impressions': Decimal('40000'), 'country': 'US', 'hour': 9L, 'utcdt': '2012-10-02'}
{'impressions': Decimal('20000'), 'country': 'US', 'hour': 9L, 'utcdt': '2012-10-02'}

为什么我本应该得到2行却得到3行？ 012-10-02应该已经汇总。

谢谢

最佳答案

之所以会得到它，是因为您按错误的值进行分组。
尝试以下方法：

SELECT DATE_FORMAT(utcdt,GET_FORMAT(DATE,'ISO')) as utcdt,
            HOUR(utcdt) as hour,
            country,
            sum(impressions) as impressions
            FROM rtb_impressions where campaign_id='cid2204184260'
            GROUP BY DATE_FORMAT(utcdt,GET_FORMAT(DATE,'ISO')), hour, country