嵌套的"CASE when“语句

Question

如何在sql查询中使用'case‘语句的嵌套形式。我正在尝试执行以下查询。

SELECT AccessTabF1.Month, AccessTabF1.Year, AccessTabF1.[Entity Number], 
case when [Exp Year]= 2010 + 1
     then 'Expires in 1 to 5 Years'
     else
          case when [Exp Year]>2010 + 5
               then 'Expires After 5 Years'
               else 'No Expiration Year Listed' 
end
from AccessTabF1

Answer 1

在您的例子中，您不需要嵌套多个case表达式。

SELECT AccessTabF1.Month, AccessTabF1.Year, AccessTabF1.[Entity Number], 
case when [Exp Year] = 2010 + 1 -- why not = 2011 ?
     then 'Expires in 1 to 5 Years' -- this does not match the logic on line above
     when [Exp Year] > 2010 + 5 -- why not > 2015 ?
     then 'Expires After 5 Years'
     else 'No Expiration Year Listed' 
end
from AccessTabF1