请帮忙修改此SQL，

[leon51]

下图中想统计每个PN中"StepD"出现的次数, 没有“StepD”的就显示0，
使用下面的语句只能得到有"StepD"的PN，请问应该怎么修改？谢谢

select pn, count(*) cnt
from table1
where step = 'StepD'
group by pn

[yaiger]

select pn, sum(decode(step, 'StepD', 1, 0))
from table1
group by pn;

Try it

[Mricoo_周]

1楼正解 而且思路非常清晰

[weixin_44200964]

select pn, sum(case when step = 'StepD' then 1 else 0 end case) sum_cnt from table1 group by pn