SQL效率日期範圍或單獨的表格

Question

我正在計算曆年數據（以2015-2016年，2014-2015年等數據爲例）如果更高效地實現它，我想尋求專業知識一次批量或多次重複查詢所需的日期過濾。

在此先感謝！

選項1：

select 
    id, 
    sum(case when year(getdate()) - year(txndate) between 5 and 6 then amt else 0 end) as amt_6_5, 
    ... 
    sum(case when year(getdate()) - year(txndate) between 0 and 1 then amt else 0 end) as amt_1_0, 
from 
    mytable 
group by 
    id 

選項2：

select 
    id, sum(amt) as amt_6_5 
from 
    mytable 
group by 
    id 
where 
    year(getdate()) - year(txndate) between 5 and 6 

... 

select 
    id, sum(amt) as amt_1_0 
from 
    mytable 
group by 
    id 
where 
    year(getdate()) - year(txndate) between 0 and 1 

Answer 1

這可能是幫助你，

WITH CTE 
AS 
(
    SELECT id, 
      (CASE WHEN year(getdate()) - year(txndate) BETWEEN 5 AND 6 THEN 'year_5-6' 
        WHEN year(getdate()) - year(txndate) BETWEEN 4 AND 5 THEN 'year_4-5' 
        ... 
        END) AS my_year, 
      amt 
    FROM mytable 
) 
SELECT id,my_year,sum(amt) 
FROM CTE 
GROUP BY id,my_year 

這裏，CTE裏面，只是分配一個合適的year_tag每個記錄（根據您的條件），然後選擇按該年份標籤分組的CTE摘要。

Answer 2

1. 除非您遇到資源問題，否則我會使用CASE版本。
雖然它對結果沒有影響，但在WHERE子句中過濾請求的時間段可能會有顯着的性能優勢。
2.您的期限定義創建重疊。

select id 
     ,sum(case when year(getdate()) - year(txndate) = 6 then amt else 0 end) as amt_6 
     -- ... 
     ,sum(case when year(getdate()) - year(txndate) = 0 then amt else 0 end) as amt_0 
where  txndate >= dateadd(year, datediff(year,0, getDate())-6, 0) 
from  mytable 
group by id