SQL存儲過程 - 試圖通過日期和if語句

Question

區分我有貨幣分類匯率的名單，我需要以某種方式發佈的關於價值的差異。

例如：

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

我希望發生什麼;當查詢運行時，它會自動計算出最新的日期，比較這一點，當前一個日期採取，並回傳一個值，說如果這已經增加，即如果增加然後「^」，如果減少「v」 ，如果相同「< - >」。

我目前的查詢可以提取最新的日期，但我仍然需要做一個子查詢來取出第二個最新的日期和值，然後發佈一個if語句。

難道我吠叫了我的方法正確的樹？

這是我的代碼。

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 

一些樣本數據：

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，你可以嘗試在接受答案的變化你前面的問題：

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 

這是沒有必要有WHERE a.RowNum = 1，如果沒有它，它只會返回其前一個值旁邊的所有記錄。