mysql - SQL Server : Select rows with dates that correspond to end of year and calculate price

Question

我有一个数据表:

  ProductNum |   ProductVariation |   Past_Price  | Current_Price  |     Order_Date       
 ------------  ------------------    ------------  ---------------  --------------------- 
       1                 33              96.05          100.10       2014-01-01 00:00:00  
       1                 33              97.65          100.10       2014-12-03 12:34:52  
       1                 33              98.98          100.10       2015-01-02 05:50:32  
       1                 33              99.98          100.10       2016-03-02 06:50:43  
       1                 33              100.01         100.10       2016-12-12 06:05:43  
       1                 33              100.05         100.10       2017-01-02 05:34:43 

我想知道是否可以查询行，以便我们获得日期最接近 12 月 31 日，{Year} 的行？

所以输出将是:

ProductNum  | ProductVariation  | Past_Price |  Current_Price   |  Order_Date       
------------ ------------------ ------------   ---------------    --------------------- 
       1                 33        98.98          100.10           2015-01-02 05:50:32  
       1                 33        99.98          100.10           2016-03-02 06:50:43  
       1                 33       100.01          100.10           2017-01-02 05:34:43  

每个订单最接近 {Year} 12 月 31 日，年份:2014,2015,2016

Answer 1

您可以按日期差异排序并获取每年的前 1 行。
对于SqlServer:

DECLARE @year2014 datetime2 = '2014-12-31 12:00:00';
DECLARE @year2015 datetime2 = '2015-12-31 12:00:00';
DECLARE @year2016 datetime2 = '2016-12-31 12:00:00';

select * from (
  select top(1) * from products
  order by abs(datediff(second, @year2014, Order_Date))
) as p    
union all
select * from (
  select top(1) * from products
  order by abs(datediff(second, @year2015, Order_Date))
)as p    
union all
select * from (
  select top(1) * from products
  order by abs(datediff(second, @year2016, Order_Date))
) as p

根据需要更改 12 月 31 日的时间。
对于MySql:

set @year2014 = '2014-12-31 12:00:00';
set @year2015 = '2015-12-31 12:00:00';
set @year2016= '2016-12-31 12:00:00';

select * from (
  select * from products
  order by abs(TIMESTAMPDIFF(second, @year2014, Order_Date)) limit 1
) as p    
union all
select * from (
  select * from products
  order by abs(TIMESTAMPDIFF(second, @year2015, Order_Date)) limit 1
)as p    
union all
select * from (
  select * from products
  order by abs(TIMESTAMPDIFF(second, @year2016, Order_Date)) limit 1
) as p