mysql 类switch case 语句case when用法

CASE attrid 
   WHEN FIND_IN_SET('7' ,attrid)>0 THEN 7 
   WHEN FIND_IN_SET('9' ,attrid)>0 THEN 9 
   WHEN FIND_IN_SET('10' ,attrid)>0 THEN 10 
   ELSE 999 
END AS spotlevel