SQL存储过程 - 试图通过日期和if语句

Question

区分我有货币分类汇率的名单，我需要以某种方式发布的关于价值的差异。

例如：

• GBP USD至|截获日期：23/02/12 |值：5
• GBP USD至|截获日期：22/02/12 |值：3
• GBP USD至|截获日期： 21/02/12 |值：3

我希望发生什么;当查询运行时，它会自动计算出最新的日期，比较这一点，当前一个日期采取，并回传一个值，说如果这已经增加，即如果增加然后“^”，如果减少“v” ，如果相同“< - >”。

我目前的查询可以提取最新的日期，但我仍然需要做一个子查询来取出第二个最新的日期和值，然后发布一个if语句。

难道我吠叫了我的方法正确的树？

这是我的代码。

SELECT 
distinct t.source_currency_code, t.target_currency_code, 
t.entry_no as entry_no, 
'(' + t.source_currency_code + ') ' + s.currency_name as source_currency_name, 
'(' + t.target_currency_code + ') ' + x.currency_name as target_currency_name, 
t.value_amount as value_amount, 
t.uplift_percent as uplift, 
t.date_loaded as date_loaded 

from texchange_rate t, tcurrency s, tcurrency x 

where 
s.currency_code = t.source_currency_code and 
x.currency_code = t.target_currency_code and 
t.date_loaded in 
     (
      SELECT max(date_loaded) from texchange_rate tt 
      where t.source_currency_code = tt.source_currency_code 
      and t.target_currency_code = tt.target_currency_code 
    ) 

order by source_currency_code, target_currency_code 


SELECT 
distinct t.source_currency_code, t.target_currency_code, 
t.entry_no as entry_no, 
'(' + t.source_currency_code + ') ' + s.currency_name as source_currency_name, 
'(' + t.target_currency_code + ') ' + x.currency_name as target_currency_name, 
t.value_amount as value_amount, 
t.uplift_percent as uplift, 
t.date_loaded as date_loaded2 

from texchange_rate t, tcurrency s, tcurrency x 

where 
s.currency_code = t.source_currency_code and 
x.currency_code = t.target_currency_code and 
t.date_loaded in 
     (
      SELECT max(date_loaded) from texchange_rate tt 
      where t.source_currency_code = tt.source_currency_code 
      and t.target_currency_code = tt.target_currency_code 
    ) 
    and 
     t.value_amount in 
     (
      SELECT value_amount from texchange_rate tt 
      where DATEDIFF(day, date_loaded, getdate()) < date_loaded 
      and t.source_currency_code = tt.source_currency_code 
      and t.target_currency_code = tt.target_currency_code 
    ) 

order by source_currency_code, target_currency_code 

一些样本数据：

4366 GBP USD 15986 23/01/2012 13:42:02 
4337 GBP USD 15600 17/10/2011 12:37:58 
4312 GBP USD 15500 22/08/2011 14:00:01 
4287 GBP USD 15500 21/08/2011 14:00:01 

Answer 1

或者，你可以尝试在接受答案的变化你前面的问题：

select source_currency_code, 
     target_currency_code, 
     max(source_currency_name) source_currency_name, 
     max(target_currency_name) target_currency_name, 
     max(case when rn = 1 then value_amount end) value_amount, 
     max(case when rn = 1 then uplift end) uplift, 
     max(case when rn = 1 then date_loaded end) date_loaded, 
     case sign(max(case when rn = 1 then value_amount end) - 
       max(case when rn = 2 then value_amount end)) 
      when 1 then '^' 
      when 0 then '<->' 
      when -1 then 'v' 
     end change_over_previous 
from 
(select t.source_currency_code, 
     t.target_currency_code, 
     '('+t.source_currency_code+') ' + s.currency_name as source_currency_name, 
     '('+t.target_currency_code+') ' + x.currency_name as target_currency_name, 
     t.value_amount as value_amount, 
     t.uplift_percent as uplift, 
     t.date_loaded as date_loaded, 
     rank() over (partition by t.source_currency_code, 
            t.target_currency_code 
        order by t.date_loaded desc) rn 
from texchange_rate t 
join tcurrency s on s.currency_code = t.source_currency_code 
join tcurrency x on x.currency_code = t.target_currency_code) v 
where rn in (1, 2) 
group by source_currency_code, target_currency_code 
order by source_currency_code, target_currency_code 

Answer 2

;WITH ExchangeCTE AS 
( SELECT *, ROW_NUMBER() OVER(PARTITION BY source_currency_code, target_currency_code ORDER BY date_loaded DESC) [RowNum] 
    FROM texchange_rate 
) 
SELECT a.source_currency_code, 
     a.target_currency_code, 
     a.entry_no AS entry_no, 
     '(' + a.source_currency_code + ') ' + s.currency_name AS source_currency_name, 
     '(' + a.target_currency_code + ') ' + t.currency_name AS target_currency_name, 
     a.value_amount AS value_amount, 
     a.uplift_percent AS uplift, 
     a.date_loaded AS date_loaded2, 
     b.value_amount AS Previous_Value_Amount, 
     CASE WHEN a.value_amount > b.value_amount THEN '^' 
      WHEN a.value_amount = b.value_amount THEN '<->' 
      ELSE 'v' 
     END AS [Symbol] 
FROM ExchangeCTE a 
     INNER JOIN ExchangeCTE b 
      ON a.source_currency_code = b.source_currency_code 
      AND a.target_currency_code = b.target_currency_code 
      AND a.RowNum = b.RowNum - 1 -- PREVIOUS RECORD 
     INNER JOIN tcurrency s 
      ON a.source_currency_code = S.currency_code 
     INNER JOIN tcurrency t 
      ON a.target_currency_code = S.currency_code 
WHERE a.RowNum = 1 -- LATEST RECORD 

这是没有必要有WHERE a.RowNum = 1，如果没有它，它只会返回其前一个值旁边的所有记录。