Question

我是一个相对新手，我现在已经和这个人争斗太久了 - 所以请任何人帮忙！

我有一个表格，可以接收不同类型开发项目的查询（dev_enquiry），我正在创建一个动态图表来显示每个开发项目每天的查询次数。我加入了日历表，其中包含一列日期，以便在没有查询时可以获得0值。

这个SQL给了我我想要的东西，但它适用于所有的开发

SELECT    calendar.datefield AS DATE, COUNT(de_id) AS enquiries
FROM      `calendar`  
LEFT JOIN dev_enquiry ON DATE(dev_enquiry.de_date_created) = calendar.datefield)
WHERE     calendar.datefield BETWEEN (
                                       SELECT MIN(DATE(de_date_created)) 
                                       FROM   dev_enquiry
                                      ) 
      AND (SELECT MAX(DATE(de_date_created)) FROM dev_enquiry)
GROUP BY  DATE 
ORDER BY  DATE DESC

2012-11-08      3
2012-11-07      0
2012-11-06      2
2012-11-05      1
2012-11-04      3

我希望按开发类型过滤掉结果，但在当天没有针对该特定开发的查询时仍保留空值。

以下过滤结果但不给我空值：

SELECT  cal.datefield AS DATE, COUNT(t.de_id)  AS  enquiries
  FROM (
SELECT * FROM dev_enquiry as d LEFT JOIN calendar as c ON (DATE(d.de_date_created) = c.datefield) 
WHERE     d.de_dev_name = 'Green') as t
LEFT JOIN calendar as cal ON (cal.datefield = DATE(t.de_date_created)) 
 WHERE (cal.datefield BETWEEN (SELECT   MIN(DATE(t.de_date_created)) 
FROM dev_enquiry) AND (SELECT MAX(DATE(de_date_created)) FROM dev_enquiry)) 
GROUP BY DATE ORDER BY  DATE  DESC


2012-11-08      1
2012-11-06      2
2012-11-05      1
2012-11-04      1

2012-11-07的结果不见了

Answer 1

这里的技巧是使用完整的日历表引导您的查询，然后加入不完整（缺少某些天）的摘要表。另请注意IFNULL将（null）结果转换为零。

     SELECT cal.datefield AS date, 
            IFNULL(s.enquiries, 0) AS enquiries
       FROM calendar as cal
  LEFT JOIN (
           SELECT count(*) enquiries,
                  de_date_created
             FROM dev_enquiry
            WHERE de_dev_name = 'Green'
         GROUP BY de_date_created
         ) s on s.de_date_created = cal.datefield
   WHERE cal.datefield 
            BETWEEN (SELECT MIN(de_date_created) FROM dev_enquiry)
                AND (SELECT MAX(de_date_created) FROM dev_enquiry)
   ORDER BY datefield DESC

这是一个SQL小提琴。 http://sqlfiddle.com/#!2/2db68/12/0

Answer 2

也许我误解了这个问题，为什么不在第一个查询示例中在左连接中添加AND de_dev_Name = 'Green'？

SELECT    calendar.datefield AS d, COUNT(dev_enquiry.de_id) AS enquiries
FROM      calendar
LEFT JOIN dev_enquiry ON (dev_enquiry.de_date_created = calendar.datefield AND de_dev_name = 'Green')
WHERE     calendar.datefield BETWEEN
          (SELECT MIN(DATE(de_date_created)) FROM dev_enquiry)
      AND (SELECT MAX(DATE(de_date_created)) FROM dev_enquiry)
GROUP BY  d
ORDER BY  d DESC

mysql报告每日查询按类型过滤，包括缺少分组行

2 个答案: