SQL | 聚合

Question

我的目标是得到一个这样的表：
请求：
年度处方药费用超过25的病房

ward_no | year | cost      
     w2 | 2007 | 34  
     w4 | 2007 | 160  
     w5 | 2006 | 26  
     w5 | 2007 | 33 

我会输入图片，但缺乏信誉点。

到目前为止，这是我所做的：

select      w.ward_no,
            year(pn.start_date)     as year,
            pn.quantity * d.price   as cost
from        ward w,
            patient pt,
            prescription pn,
            drug d
where       w.ward_no = pt.ward_no
        and
            pn.drug_code = d.drug_code
        and 
            pn.patient_id = pt.patient_id
group by    w.ward_no, 
            year,
            cost
having      cost > 25
order by    w.ward_no, year

我当前的输出是这样的：

    ward_no|year|cost
    'w2'   |2006|0.28
    'w2'   |2007|3.20
    'w2'   |2007|9.50
    'w2'   |2007|21.60
    'w3'   |2006|10.08
    'w3'   |2007|4.80
    'w4'   |2006|4.41
    'w4'   |2007|101.00
    'w4'   |2007|58.80
    'w5'   |2006|25.20
    'w5'   |2006|0.56
    'w5'   |2007|20.16
    'w5'   |2007|12.60

我如何将每个ward_no减少为仅一行（例如2006或2007）而不是x？
任何帮助将不胜感激，我真的很困并且不知道该怎么办。

Answer 1

您正在按成本分组，因此每个成本都有一个新行。 从分组中删除费用

select      w.ward_no,
        year(pn.start_date)     as year,
        avg(pn.quantity * d.price)   as cost
from        ward w,
        patient pt,
        prescription pn,
        drug d
where       w.ward_no = pt.ward_no
    and
        pn.drug_code = d.drug_code
    and 
        pn.patient_id = pt.patient_id
group by    w.ward_no, 
        year
having       avg(pn.quantity * d.price) > 25
order by    w.ward_no, year

Answer 2

您需要按病房和年份分组，并汇总费用：

select w.ward_no,
       year(pn.start_date) as year,
       sum(pn.quantity * d.price) as cost
  from ward w
  inner join patient pt
    on pt.ward_no = w.ward_no
  inner join prescription pn
    on pn.patient_id = pt.patient_id
  inner join drug d
    on d.drug_code = pn.drug_code
  group by w.ward_no, 
           year(pn.start_date)
  having sum(pn.quantity * d.price) > 25
  order by w.ward_no, year

这应该用于哪种SQL？

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