怎么改这个SQL语句

[520NET]

select b.field_id as cID,c.num as cTotal
from tb_field_resource b left
join (select a.psc_channel,count(a.psc_channel) num from tb_psr_check a group by a.psc_channel) c
on c.psc_channel = b.field_id
order by b.field_id
查询结果如下：
CID CTOTAL
D001 2
D002 3
D003 4
DOO4
DOO5
我想达到如下效果：
CID CTOTAL
D001 2
D002 3
D003 4
DOO4 0（没有数据写0）
DOO5 0（没有数据写0）

[Eric_1999]

select b.field_id as cID, NVL(c.num, 0) as cTotal
from tb_field_resource b left
join (select a.psc_channel,count(a.psc_channel) num from tb_psr_check a group by a.psc_channel) c
on c.psc_channel = b.field_id
order by b.field_id

用NVL就可以拉

[zqf2010]

楼上正解

[gw_delphi]

select b.field_id as cID, decode(c.num,'',0,c.num) as cTotal
from tb_field_resource b left
join (select a.psc_channel,count(a.psc_channel) num from tb_psr_check a group by a.psc_channel) c
on c.psc_channel = b.field_id
order by b.field_id

[baixiaotian]

Eric_1999(Eric) 正解