Question

我有一个表格，每天显示一个产品价格。一个产品有3个价格：批发价，数量和清仓价。

该表每天都用当前价格进行更新，大多数日子没有变化。但是，我想选择其中一个值已更改的行，而我正在努力寻求构想。我试过了一个小组，但是因为价格涨跌，这行不通。

select date_entered, 
       WholeSale,
       Volume,
       Clearance 
FROM pricetable 
where product = 'TANGO'
order by date_entered desc

以上内容从表格中为已设置产品选择所有行。

如何做到这一点，所以只能进行更改，批发，数量或清仓的行。

任何帮助表示赞赏。

Answer 1

该问题最初是带标签的SQL-SERVER（无版本）。这适用于SQL Server 2012 +：

使用lag()。像这样：

select pt.*
from (select pt.*,
             lag(wholesale) over (partition by product 
                                  order by date_entered) as prev_wholesale,
             lag(volume)    over (partition by product 
                                  order by date_entered) as prev_volume,
             lag(clearance) over (partition by clearance 
                                  order by date_entered) as prev_clearance
      from pricetable
      where product = 'TANGO'
     ) pt
where (prev_wholesale is null or prev_wholesale <> wholesale) or
      (prev_volume is null or prev_volume <> volume) or
      (prev_clearance is null or prev_clearance <> clearance)          
order by date_entered desc;

Answer 2

select p1.date_entered, 
       p1.WholeSale,
       p1.Volume,
       p1.Clearance 
FROM pricetable p1
CROSS APPLY
--cross apply to most recent prior record
(SELECT TOP 1 * 
        FROM pricetable p2 
            where p1.product = p2.product 
                and p2.date_entered < p1.date_entered 
                    order by p2.date_entered desc) CA
where p1.product = 'TANGO'
  and (p1.wholesale != CA.wholesale or p1.volume != CA.volume or p1.clearence != CA.clearence)
order by p1.date_entered desc

Answer 3

将每一行的值与前一天的值进行比较：

SELECT * FROM pricetable p WHERE (p.product = 'TANGO') AND
(
    (p.WholeSale <> (SELECT WholeSale FROM pricetable WHERE product = 'TANGO' AND date_entered = dateadd(day, -1, p.date_entered))
OR
    (p.Volume <> (SELECT Volume FROM pricetable WHERE product = 'TANGO' AND date_entered = dateadd(day, -1, p.date_entered))
OR
    (p.Clearance <> (SELECT Clearance FROM pricetable WHERE product = 'TANGO' AND date_entered = dateadd(day, -1, p.date_entered))
)

选择值已更改的行

3 个答案: