case语句按条件更新数据列

update s_dr
set dpt_no = (
select dpt_no = 
case
when dpt_name = '保健科' then 'K0001'
when dpt_name = '便民门诊' then 'K0002'
when dpt_name = '大内科（普内科）' then 'K0003'
when dpt_name = '风湿免疫科' then 'K0004'
end
from s_dr a
where s_dr.id=a.id
)