sql decode和case when如何转换

Question

select max(decode(c.code,'001',b.ratio)) rt1,
max(decode(c.code,'002',b.ratio)) rt2,
max(decode(c.code,'003',b.ratio)) rt3,
from table1 a
left join table2 b on a.billid=b.ruleid
left join table3 c on a.sourceid=c.billid
group by a.projectid,a.economicid, b.bdgagency
问一下这个decode怎么转换成case when的形式啊

Answer 1

 decode(c.code,'001',b.ratio)
 =
 case c.code 
 when '001' then b.ratio
 end