Question

我在SQL（2012）数据库上运行查询，该数据库返回给定日期范围内的记录数，按日期分组。

例如：

Date    Count
12/08   12
14/08   19
19/08   11

我需要填写空白作为我绘制的图表因为缺少值而被搞砸了。有没有办法强制SQL报告一个空行，或者当它没有遇到结果时为“0”值？

我的查询是

SELECT TheDate, count(recordID) 
FROM myTable 
WHERE (TheDate between '12-AUG-2013 00:00:00' and '20-AUG-2013 23:59:59')
GROUP BY TheDate

我是否需要创建一个包含记录的临时表，然后从中选择并右键加入来自myTable的任何记录？

感谢您的帮助！

Answer 1

如果您创建日期范围的（临时或永久）表格，则可以left join到结果中创建包含空白的结果集

 SELECT dates.TheDate, count(recordID) 
 FROM 
 ( select 
      convert(date,dateadd(d,number,'2013-08-12')) as theDate 
   from master..spt_values 
   where type='p' and number < 9
 ) dates
 left join yourtable on dates.thedate = convert(date,yourtable.thedate)
 GROUP BY dates.TheDate

Answer 2

临时表可以完成这项工作，但是对于这么小的日期范围，您可以更简单地使用UNION - ed子查询。 E.g：

SELECT dates.TheDate, ISNULL(counts.Records, 0)
FROM
(SELECT TheDate, count(recordID) AS Records
 FROM myTable 
 WHERE (TheDate between '12-AUG-2013 00:00:00' and '20-AUG-2013 23:59:59')
 GROUP BY TheDate
) counts
RIGHT JOIN
(SELECT CAST('12-AUG-2013' AS DATETIME) AS TheDate
 UNION ALL SELECT CAST('13-AUG-2013' AS DATETIME) AS TheDate
 UNION ALL SELECT CAST('14-AUG-2013' AS DATETIME) AS TheDate
 UNION ALL SELECT CAST('15-AUG-2013' AS DATETIME) AS TheDate
 UNION ALL SELECT CAST('16-AUG-2013' AS DATETIME) AS TheDate
 UNION ALL SELECT CAST('17-AUG-2013' AS DATETIME) AS TheDate
 UNION ALL SELECT CAST('18-AUG-2013' AS DATETIME) AS TheDate
 UNION ALL SELECT CAST('19-AUG-2013' AS DATETIME) AS TheDate
 UNION ALL SELECT CAST('20-AUG-2013' AS DATETIME) AS TheDate
) dates
ON counts.TheDate = dates.TheDate

这是SQL Fiddle Demo。

如果您需要更通用（但也更复杂）的解决方案，请查看this excellent answer（@RedFilter）查询类似问题。

强制在SQL查询的日期范围内返回的行数

2 个答案: