[英]Grouping by multiple columns in SQL
我正在嘗試通過site.Site_Name來獲取每個hive.hiveno及其最大值(hiverdg.invdate)。 由於site.Site_Name未凝結,因此無法運行下面的代碼。 如果我將site.Site_Name添加到分組依據,則代碼將運行,但輸出將重復顯示結果,每個站點一次。
select site.Site_Name ,hive.hiveno, max(hiverdg.invdate)
from hiverdg
inner join hive
on hiveRdg.hive_Link = hive.hive_Link
inner join Customer
on customer.Customer_Link = hive.Customer_Link
inner join site
on site.Customer_Link = customer.Customer_Link
where
(hiverdg.xtype = 'N'
and customer.CustomerName = 'Cust1')
or
(hiverdg.xtype = 'A'
and customer.CustomerName = 'Cust1')
group by hive.hiveno
使用查詢執行此操作的最簡單方法是substring_index()
/ group_concat()
技巧:
select substring_index(group_concat(s.Site_Name order by rdg.invdate desc separator '|'
), '|', 1
) as SiteName,
h.hiveno, max(rdg.invdate)
from hiverdg rdg inner join
hive h
on rdg.hive_Link = h.hive_Link inner join
Customer c
on c.Customer_Link = h.Customer_Link inner join
site s
on s.Customer_Link = c.Customer_Link
where rdg.xtype in ('N', 'A') and c.CustomerName = 'Cust1')
group by h.hiveno;
我還對您的查詢進行了以下更改:
where
使用in
,簡化了邏輯。
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