基于第一个的第二个 sql 查询

Question

i want to take the result of an sql query "user_id"and search using it in in another query in another table for example :

main query select * from tracker second query: take the id from the first query to replace it with the name of the user found in another table "user table". something like : select user_name from vtiger_users where id = $row["id"]

here is my code below

    <?php
    $servername = "localhost";
    $username = "x";
    $password = "xyz";
    $dbname = "dbname";

    // Create connection
$conn = new mysqli($servername, $username, $password, $dbname);
// Check connection
if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
} 

$sql = "SELECT id, module, whodid,changedon FROM vtiger_modtracker_basic";
$result = $conn->query($sql);


if ($result->num_rows > 0) {


    echo "<table style='float: left'><tr><th>ID</th><th>Module</th><th>Who Did</th><th>Time Of Action</th></tr>";
    // output data of each row

    while($row = $result->fetch_assoc()) {
        $user_id=$row["id"];
        $username_sql="SELECT user_name FROM vtiger_users where id=".$user_id." ";
        $result_username=$conn->query($username_sql);
        $row2 = $result_username->fetch_assoc();


        echo "<tr><td>".$row["id"]."</td><td>".$row["module"]."</td><td>".$row2["user_name"]."</td><td>".$row["changedon"]."</td></tr>";




        //echo "<p>".$row2["user_name"]."</p>"





        //echo $row2["user_name"];


    }
    echo "</table>";
} else {
    echo "0 results";
}
$conn->close();
?>

Answer 1

I guess you should use whodid column when you set $user_id = $row['whodid'] or you can use JOIN query. It will return you user_name from vtiger_users table.

SELECT
    a.id,
    a.module,
    a.whodid,
    a.changedon 
    b.user_name
FROM vtiger_modtracker_basic a
JOIN vtiger_users b ON a.whodid = b.id

Answer 2

谢谢大家，那个查询为我完成了工作

SELECT vtiger_modtracker_basic.id, vtiger_modtracker_basic.module, vtiger_modtracker_basic.whodid ,vtiger_modtracker_basic.changedon ,vtiger_users.user_name FROM vtiger_modtracker_basic ,vtiger_users where vtiger_modtracker_basic.whodid = vtiger_users.id