mysql 将查询出来的值进行转换

如下：

 

 

 mysql支持if  
   
  SELECT   IF(1<2,'yes','no');  
  输出yes  
   
  同时，还支持case  
   
  SELECT   CASE   WHEN   1>0   THEN   "yes"   ELSE   "no"   END;  
  还是输出yes  

 

 

select c1.*,if(c2.total is null,0,c2.total)total from channel_class c1 left join
(select count(*) total,PARENT_ID from channel_class group by PARENT_ID HAVING PARENT_ID>0) c2
on c2.PARENT_ID = c1.class_id