Weird MYSQL results using PDO::FETCH_ASSOC without column alias

Question

I have a simple left join query.

SELECT e.employee_id as employee
, e.badge_id as badge
, e.first_nm as first
, e.last_nm as last
, e.work_phone as work_ph
, e.mobile_phone as mobile_ph
, e.manager_id as man_id
, e.title_id as titl_id
, e.username as user
, e.start_dt as start
, m.employee_id as memp_id
, m.last_nm as m_last
, m.first_nm as m_first
, t.title_nm as titl_nm
FROM employee e
left join employee m
on e.manager_id = m.employee_id
left join title t
on e.title_id = t.title_id
WHERE e.employee_id = 1

If I use column aliases as I have done above, the query works fine. If I do not use aliases, however, some values do not get returned. For example, the following returns a space if I do not give the column an alias.

e.first_nm as first      //returns "Robert"
e.first_nm               //returns ""
e.first_nm as first_nm   //returns "" (alias matches column name)

In this same query,

e.middle_nm              //will return "P" 

regardless of whether it has an alias or not. I'm baffled.

I have given my tables aliases and I have used the table alias in the column names so there shouldn't be any ambiguous column names.

Any thoughts would be appreciated. Thanks,

Rob

Answer 1

You have two columns with same name as first_nm and problably the PDO don´t know what return to your code then return simple "". Although they are in diferent tables when came to a record they have the same name... you see the problem?

Answer 2

You have two columns with same name as first_nm and mysql knows how to return them all right, and then return simple "first_nm" for both. And then PDO have to assign them to array members, making field names as array keys. There is only one way, like this

$row['first_nm'] = first col;
$row['first_nm'] = second col;

If you try to see into $row, how many entries you will find?

So, you either have to use FETCH_ROW or give your fields distinct names. It's neither mysql nor PDO to blame - it's just how the things work.