Try to select null as columnName with table alias

Question

I am having an issue where I am working on table aliases and ran into a weird issue. I am able to use null as column name when I am not using table alias, but if I use a table alias I run into issues.

works!

select top 10 eid, null as emp_no from employee 

does not work!!

select top 10 e.eid, null as e.emp_no from employee e

Is there a way out? I am running into an issue when I join with another table.

Trying to make it work !

select top 10 e.eid, null as e.emp_no, ed.desgination from employee e 
inner join employee_designations ed on e.eid=ed.eid


Error 

Msg 102, Level 15, State 1, Line 1
Incorrect syntax near '.'.

Answer 1

Try:

select top 10 e.eid, null as emp_no from employee e

You can alias NULL, but SQL will throw a hissy-fit if you claim that it's from table alias e.

UPDATE:

To use the NULL in a join, turn it into a subquery:

SELECT  e.eid
        , e.emp_no
FROM    (
            SELECT  TOP 10 eid
                    , NULL AS emp_no
            FROM    employee
        ) AS e

Alias your subquery as e and now SQL will happily accept NULL as e.emp_no.