SQL查询要做除法

Question

请帮助解决下面的SQL查询，它将第一组查询与第二组查询分开。

SELECT 
FROM 
(
  SELECT `Business_Unit`, 
   COUNT(`Joining_Month`) AS A 
  FROM `jl` 
  WHERE `Final_Status` = 'Joined' 
   AND `Source_wise` = 'Referral' 
   AND `Hiring_Catg` IN ('Lateral','Contract Conversion') 
  GROUP BY `Business_Unit`
) 
DIV 
(
  SELECT `Business_Unit`, 
   COUNT(`Joining_Month`) AS B 
  FROM `jl` 
  WHERE `Final_Status` = 'Joined' 
   AND `Hiring_Catg` IN ('Lateral','Contract Conversion') 
  GROUP BY `Business_Unit`
) ;