Sql Script for blank values

Question

I have uploaded a bulk data having 20 columns.

 

in SQL am trying to bind 3 column join against the employee master.

 

For Example

 

select * from #temptable

 

select  tmp.*

 from #temptable tmp , employeemaster em

where em.employeeno= tmp.Employeeno1 and

           em.employeeno= tmp.Employeeno2 and

          em.employeeno= tmp.Employeeno3 

 

the above query will return  records if all the condtion are matched in the where clause.

But lets say am passing the value only for  tmp.Employeeno1 =123 and tmp.Employeeno2=456

and tmp.Employeeno3 as empty record.

Its a valid records how can i allow it in my script using blank or null values.