oracle中decode()函数在mysql中如何改啊

oracle中decode()函数在mysql中怎么改啊，在线等！
例如在oracle中是这样写的：select
decode(length(POPEDOM),3,substr(POPEDOM,0,2),4,substr(POPEDOM,0,3),5,substr(POPEDOM,0,2),6,substr(POPEDOM,0,3),7,substr(POPEDOM,0,2),POPEDOM) as type

------解决方案--------------------
MYSQL没用过，不过我想case when then应该也是支持的吧：
SELECT (CASE length(POPEDOM)
         WHEN 3 THEN
          substr(POPEDOM, 0, 2)
         WHEN 4 THEN
          substr(POPEDOM, 0, 3)
         WHEN 5 THEN
          substr(POPEDOM, 0, 2)
         WHEN 6 THEN
          substr(POPEDOM, 0, 3)
         WHEN 7 THEN
          substr(POPEDOM, 0, 2)
       END) AS TYPE
  FROM DUAL;