sql - 每月动态创建列计数

Question

好的，所以我有这个查询来查找每天的类型数量，如下所示。（此处由 MarkD 提供Counting Items/Rows in DB as Columns Grouped by another Column）

 select type,
           sum(case when MyDate = '' then 1 else 0 end) as "10/1",
           sum(case when MyDate = '' then 1 else 0 end) as "10/2
           ...etc
 from MyTabe
 group by type

但是，我想动态创建日期列并为每列生成计数，否则我最终会为每个月的每一天手动添加一个新列。

Answer 1

我想获得我想要的输出的最佳方法是执行以下操作：

 define startDate = to_date('2013-10-01', 'yyyy-mm-dd')
 select type,
       sum(case when MyDate = &&startDate then 1 else 0 end) as "1"
       , sum(case when MyDate = &&startDate +1 then 1 else 0 end) as "2"
       , sum(case when MyDate = &&startDate +2 then 1 else 0 end) as "3"
       , sum(case when MyDate = &&startDate +3 then 1 else 0 end) as "4"
       ...etc for as many days of current month I am running
       , sum(case when MyDate = &&startDate +29 then 1 else 0 end) as "30"   
       , sum(case when MyDate = &&startDate +30 then 1 else 0 end) as "31"--This would be commented out for Nov  
 from MyTabe
 group by type
 order by type
 ;

这样，如果我想在 11 月、12 月、1 月等时间运行它，我只需更改顶部的变量并运行查询。这就是我一直在寻找的；但是，我仍然想知道是否可以动态生成列，但是我越看它，我就越认为需要数据透视表。