如何回显具有相同ID的多行

Question

I have a database that allows a user id to appear as many times as the user wants eg id = 1902 the items belonging to this id is fish, bread, milk. Same user has with same id on another row id = 1902 the items belonging to this id row is pepper, mat, mouse.

I want to try and output the user id and all its items but don't know the code to use on this.

<?php
$xyttt = $_SESSION['email'];

$sql = "SELECT id FROM users where username = '$xyttt'";

$result = mysqli_query($db, $sql);

// fetch the resulting rows as an array
$investment = mysqli_fetch_all($result, MYSQLI_ASSOC);
foreach($investment as $invest){ 
    // echo ($invest['id']); 
    $uidbb = ($invest['id']);
} 

// free the $result from memory (good practise)
mysqli_free_result($result);

$uidbb = ($invest['id']);

$sql = "SELECT * FROM investment where userid = '$uidb'";

$result = mysqli_query($db, $sql);

if ($result->num_rows > 0) {
    // output data of each row
    while($row = $result->fetch_assoc()) {
        echo "id: " . $row["id"]. " - Name: " . $row["amount1"]. " " . $row["status"]. "<br>";
    }
} else {
    echo "0 results";
}

$conn->close();
// free the $result from memory (good practise)
mysqli_free_result($result);

?>

I used this code but it was fetching all the rows of the database including the id of other users but I want it to fetch all rows of just a particular id that appears as many times on the table.

Answer 1

You can get all items and user id from one request SQL

SELECT * FROM investment where userid = (SELECT id FROM users WHERE username = ?)

OR

SELECT 
* 
FROM 
    investment INV
INNER JOIN
    users U ON U.id = INV.userid
WHERE U.username = ?

To select custom rows you must replace ( * ) by the desired value from table

I did not understand your problem very well:/

Answer 2

You can do it in one query using an inner join, something like this:

SELECT 
    * 
FROM 
    investment 
INNER JOIN
    users ON users.id = investment.userid
WHERE users.username = ?

That will fetch all records from investment that has the username you provide.

You can read more about inner joins here: https://www.mysqltutorial.org/mysql-inner-join.aspx/

Note

As you can see, both me and the other answer use ? instead of the variable with the username. That's because we use parameterized prepared statements instead of injecting data directly into the queries. I would recommend that you read through that as well, since it's the recommended way of using dynamic data in your queries (and is a necessity when working with external data)