what is mistake int this statement

c.* is the problem here. As you are using Group By clause, you have to mention only specific column names in your select list that are in group by.

Try this instead.

select p.empid,COUNT(p.empid) 
from empcdetails c 
inner join emppdetails p 
on p.empid=c.empid 
where empstatus = 'project' 
group by p.empid 
order by MAX(c.empdoj)asc

Try this subquery version, if you want to have all columns

select c.* , A.myCount
from empcdetails  c
join 
(
	select p.empid,COUNT(p.empid) as myCount
	from empcdetails cc 
	inner join emppdetails p 
	on p.empid = cc.empid 
	group by p.empid 
) A
on A.empid = c.empid
where empstatus = 'project' 
order by MAX(c.empdoj)asc

Hope this helps you.