根据会计年度和期间选择字段

Question

我使用的表格有一个金额字段、一个会计年度和一个期间字段（以及其他字段）。我需要根据会计年度和期间字段选择两次金额字段。我遇到的问题是如何编写 SQL 来选择 2014 财年和第 10 期的记录作为先前金额的记录。我还需要确保它适用于 2014 / 01 并且之前的时间段是 2013 / 12。感谢您的帮助......

SELECT 
a.business_unit,
a.amount as CURRENT_AMOUNT,
a.amount as PRIOR_AMOUNT,
a.fiscal_year as FY,
a.period as AP

FROM Asset_Depreciation a

WHERE
a.business_unit = 'A0001'
AND a.fiscal_year = 2014
AND a.period = 11

结果 A0001 500.00（空白）2014 11

Answer 1

您可以使用lag()解析函数找到之前的amount。您可以使用子查询在where 过滤器之前应用lag()：

select  prevamount
,       business_unit
,       curamount
,       fiscal_year
,       period
from    (
        select  lag(amount) over (
                    partition by business_unit
                    order by fiscal_year, period) as prevamount
        ,       business_unit
        ,       amount as curamount
        ,       fiscal_year
        ,       period
        from    Asset_Depreciation
        ) SubQueryAlias
where   business_unit = 'A0001'
        and fiscal_year = 2014
        and period = 11

如果没有子查询，lag() 将只查看一行而不找到任何先前的值。

Working example at SQL Fiddle.