使用Inner Join MySQL php从3表中获取数据

Question

include '../incs/connect.php';
    $q=mysqli_query($con,"SELECT appl_reg_details.appl_id, appl_reg_details.apl_name, appl_reg_details.apl_email, rp_test_result.appl_status, rp_intv_result.intv_obt_marks
                          FROM appl_reg_details
                          INNER JOIN rp_test_result ON appl_reg_details.appl_id = rp_test_result.appl_id
                          INNER JOIN rp_intv_result ON rp_test_result.appl_id = rp_intv_result.appl_id
                          GROUP BY appl_reg_details.appl_id
                          ");
    WHILE($row=mysqli_fetch_array($q))
    {
        echo $row=['appl_id']." - ";
        echo $row=['apl_name']." - ";
        echo $row=['intv_obt_marks']." - ";
        echo $row=['appl_status']." -";
        echo $row=['apl_email']."<br/>";
    }

I have 3 tables and i want to get data of 3 field from table1, of 1 field from table 2 and table 3 each, i have found that inner join can do this, when i run this it says 'Notice: Array to string conversion', help to correct this or give a new way please

Answer 1

The query looks fine at first glance.

The problem is with the lines below it. They include an unnecessary = :

echo $row=['apl_email']."<br/>";

These lines should be like this:

echo $row['apl_email']."<br/>";

Answer 2

Performance benefits aside, GROUP BY serves no purpose here other than to confuse the result set. Try something like this instead, and fix the coding errors identified by rjdown:

SELECT DISTINCT d.appl_id
              , d.apl_name
              , d.apl_email
              , t.appl_status
              , i.intv_obt_marks
           FROM appl_reg_details d
           JOIN rp_test_result t
             ON t.appl_id = d.appl_id 
           JOIN rp_intv_result i 
             ON r.appl_id = i.appl_id;