Question

我在Oracle中有一个表，其中包含文章的价格和日期，但是我需要上个月和当月的文章价格才能看到差异。

我需要通过上个月作为参数并获取数据

示例：

+---------+-------+------------+
| article | price | date       |
+---------+-------+------------+
| cup     | 3.5   | 02/06/2018 |
+---------+-------+------------+
| cup     | 3.7   | 04/07/2018 | 
+---------+-------+------------+
| cup     | 3.8   | 04/08/2018 | 
+---------+-------+------------+

预期：

所选月份：07

+---------+--------------+-------------+----------+----------+
| article | current_price|current_month|last_price|last_mont |
+---------+--------------+-------------+----------+----------+
| cup     |      3.7     |  07/2018    | 3.5      |  06/2018 |
+---------+--------------+-------------+----------+----------+

Answer 1

您可以使用以下SQL语句：

select article, 
       max(decode(to_char("date",'mm/yyyy'),to_char(sysdate,'mm/yyyy'),nvl(price,0)))
       as current_price,
       to_char(sysdate,'mm/yyyy') as current_month,
       max(decode(to_char("date",'mm/yyyy'),to_char(add_months(sysdate,-1),'mm/yyyy'),
                                                                nvl(price,0)))
       as last_price,
       to_char(add_months(sysdate,-1),'mm/yyyy') as last_month
  from articles 
 where article = 'cup'
group by article;

ARTICLE CURRENT_PRICE   CURRENT_MONTH   LAST_PRICE  LAST_MONTH
  cup       3,70           07/2018         3,50       06/2018

假设sysdate（当前日期）介于01/07/2018 - 31/07/2018（格式为dd/mm/yyyy）

Rextester Demo

Answer 2

假设用户指定了日期，则以下内容将获取该日期的最后两个日期和价格：

select article_id,
       max(case when seqnum = 1 then price end) as current_price,
       max(case when seqnum = 1 then date end) as current_date,
       max(case when seqnum = 2 then price end) as last_price,
       max(case when seqnum = 2 then price end) as last_date
from (select e.*,
             row_number() over (partition by article_id order by date desc) as seqnum
      from examples e
      where e.date <= :date
     ) e
group by article_id;

如何以月为参数从同一张表中获取不同的数据？

2 个答案: