有没有办法与案件联系

Question

有没有办法与案件联系？

就像是

select * from abba 
   case when a=b then 
      join acdc on abba.id=acdc.id
   when b=c then 
      join bebop on abba.id=bebop.id 
   end

有没有办法做到这一点？

最好的问候乔

Answer 1

通常的方法是LEFT JOIN两个表并根据CASE条件选择值:

SELECT *, CASE WHEN a=b THEN acdc.myField ELSE bebop.myField END AS myField
  FROM abba 
       LEFT JOIN acdc ON abba.id=acdc.id 
       LEFT JOIN bebop ON abba.id=bebop.id