SQL：根据会计年度将行拆分为多行

Question

我有一个查询，我可以生成下表，

Name    School          Department  StartDate   Enddate
John    ABC School  Math            7/1/2004    7/18/2007
John    ABC School  Science         7/1/2010    Nulll
Steve   XYZ School  English         2/1/2004    9/30/2006
Steve   XYZ School  Geology         10/1/2006   Null

我想知道有没有办法根据会计年度将每行拆分成多行

Name    School          Department  Fiscal Year
John    ABC School  Math            2005
John    ABC School  Math            2006
John    ABC School  Math    2007
John    ABC School  Science 2011
John    ABC School  Science 2012
Steve   XYZ School  English 2004
Steve   XYZ School  English 2005
Steve   XYZ School  English 2006
Steve   XYZ School  Geology 2007
Steve   XYZ School  Geology 2008
Steve   XYZ School  Geology 2009
Steve   XYZ School  Geology 2010
Steve   XYZ School  Geology 2011
Steve   XYZ School  Geology 2012

Answer 1

假设存在一个表f来定义具有开始和结束日期的会计年度，您可以使用以下内容执行此操作：

SELECT f.name, t.name FROM t
INNER JOIN f
ON f.start BETWEEN t.start AND t.end
OR f.end BETWEEN t.start AND t.end

Answer 2

您可以使用COALESCE处理NULL结束日期

SELECT f.name, t.name FROM t
INNER JOIN f
ON f.start BETWEEN t.start AND COALESCE(t.end,CURRENT_DATE)
OR f.end BETWEEN t.start AND COALESCE(t.end,CURRENT_DATE)