我正在计算不同客户的数量并按另一列对其进行分组。如果在组中找不到客户,我希望结果返回零。使用下面的代码,我的结果不会为零。有人能帮忙吗?
SELECT download_date,resolution,COUNT(DISTINCT customer_id) FROM test.sample
GROUP BY download_date,resolution;
这给了我以下信息:
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| 2011-06-09| HD | 1 |
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| 2011-06-09| SD | 1 |
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| 2012-06-10| SD | 1 |
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我希望得到以下信息:
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| 2011-06-09| HD | 1 |
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| 2011-06-09| SD | 1 |
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| 2012-06-10| HD | 1 |
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| 2012-06-10| SD | 0 |
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下面是表格结构:
CREATE TABLE test.sample (
`customer_id` VARCHAR(15) NULL DEFAULT NULL,
`download_date` DATE NULL DEFAULT NULL,
`resolution` VARCHAR(2) NULL DEFAULT NULL,
`total_units` INT(11) NULL DEFAULT NULL);
INSERT INTO test.sample(`customer_id`,`download_date`,`resolution`,`total_units`)
VALUES('1','2012-06-10','HD',40),('1','2012-06-10','HD',20),
('2','2011-06-09','SD',10),('2','2011-06-09','HD',20);
最佳答案
select dr.download_date, r.resolution,COUNT(DISTINCT customer_id)
from
(select DISTINCT download_date from sample) dr
cross join
(select distinct resolution from sample) r
left join sample s on s.download_date = dr.download_date
and r.resolution = s.resolution
group by dr.download_date, r.resolution;
FIDDLE
关于mysql - 返回零与组和在MySQL中计数,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/17750509/