where优化中的MySQL查询case语句

我正在用mysql编写一个查询，我对递归查询不太熟悉。 如何以及我需要做什么来优化下面的查询，因为我提出的条件看起来不好，必须有一个更简单的方法来做同样的事情

 select
   b.entity_id 
from
   entity_hierarchies a,
   entity_hierarchies b 
where
   a.entity_id = 25 
   and a.entity_type = 'user' 
   and b.entity_type = 'idea' 
   and a.Geography_Geography = 
   case
      when
         a.Geography_Geography is null 
      then
         a.Geography_Geography 
      else
         b.Geography_Geography 
   end
   and COALESCE(a.Geography_Country, '') = 
   case
      when
         a.Geography_Country is null 
      then
         COALESCE(a.Geography_Country, '') 
      else
         b.Geography_Country 
   end
   and COALESCE(a.Geography_DistrictOrCounty, '') = 
   case
      when
         a.Geography_DistrictOrCounty is null 
      then
         COALESCE(a.Geography_DistrictOrCounty, '') 
      else
         b.Geography_DistrictOrCounty 
   end
   and COALESCE(a.Geography_State, '') = 
   case
      when
         a.Geography_State is null 
      then
         COALESCE(a.Geography_State, '') 
      else
         b.Geography_State 
   end
   and COALESCE(a.Geography_City, '') = 
   case
      when
         a.Geography_City is null 
      then
         COALESCE(a.Geography_City, '') 
      else
         b.Geography_City 
   end

简介 我注意到你可以用更简单的形式重写其中的一些语句

例如：

and a.Geography_Geography = 
   case
      when
         a.Geography_Geography is null 
      then
         a.Geography_Geography 
      else
         b.Geography_Geography 
   end

可以简单地变成：

AND ( a.Geography_Geography is null or a.Geography_Geography =   b.Geography_Geography )

最终解决方案 简介 我注意到你可以用更简单的形式重写其中的一些语句

例如：

and a.Geography_Geography = 
   case
      when
         a.Geography_Geography is null 
      then
         a.Geography_Geography 
      else
         b.Geography_Geography 
   end

可以简单地变成：

AND ( a.Geography_Geography is null or a.Geography_Geography =   b.Geography_Geography )

最终解决方案