从查询到PHP调用别名变量

Question

$query = mysql_query("SELECT DISTINCT E.first_name, E.last_name, F.first_name,                   F.last_name
                      FROM faculty AS E, faculty AS F, evaluations_faculties 
                      WHERE evaluator_id = E.user_id
                      AND evaluee_id = F.user_id");

while( $row = mysql_fetch_assoc($query))
{
    echo $row['E.first_name'];
}

I have been trying to echo E.first_name but it does not seem to work. What will be the correct syntax to call E.first_name or F.first_name.

Answer 1

Use aliases for those variables:

$query = mysql_query("SELECT DISTINCT E.first_name as fname, E.last_name as lname, F.first_name as ffname, F.last_name as flname 
                                                   ^^^^^^^^
FROM faculty AS E, faculty AS F, evaluations_faculties 
WHERE evaluator_id = E.user_id AND evaluee_id = F.user_id");

while( $row = mysql_fetch_assoc($query))
{
  echo $row['fname'];//etc
}

And beware: mysql_ functions are deprecated and will be removed in future implementations as they bear a risk of mysql injections. Change to mysqli or PDO to get use of prepared statements which prevent against injections.

Answer 2

Its better to give a proper alias name when you have same column names repeated in the query while doing join.

SELECT DISTINCT 
E.first_name as E_firstname, 
E.last_name as E_lastname,
F.first_name as F_firstname,                   
F.last_name as F_lastname                
FROM faculty AS E, faculty AS F, evaluations_faculties 
WHERE evaluator_id = E.user_id
 AND evaluee_id = F.user_id

You can access the values at the PHP as

$row['E_firstname'] 

and so on for others

Answer 3

You should use this:

$query = mysql_query("SELECT DISTINCT E.first_name AS e_first_name, E.last_name, F.first_name AS f_first_name, F.last_name
                      FROM faculty AS E, faculty AS F, evaluations_faculties 
                      WHERE evaluator_id = E.user_id
                      AND evaluee_id = F.user_id");

while( $row = mysql_fetch_assoc($query))
{
    echo $row['e_first_name'];
}