更新 MySQL 数据库表中具有不同值的多行

Question

I'm trying to select commenter from a table called comments then select username from a table called users using a where clauses from the details from the first table. After that update comments set username to the usernames obtained from table 2.

This is my code:

<?php 
include("connection.php") ;
$sql=mysqli_query($link, "SELECT * FROM comment ORDER BY id ASC" ) ;
while($row=mysqli_fetch_assoc($sql)){
    $commenter=$row['commenter'] ;

    $sqli=mysqli_query($link, "SELECT * FROM users WHERE fullname='$commenter' ORDER BY id ASC" ) ;
    while($rows=mysqli_fetch_assoc($sqli)){
        $username=$rows['username'] ;
        $sql_u=mysqli_query($link, "UPDATE comment SET username='$username' WHERE commenter='$commenter' " ) ;
    }
}
?>

The code above only updates one row

Answer 1

Here is a small correction of Barmar answer

UPDATE comment c
JOIN users u ON u.fullname = c.commenter
SET c.username = u.username

u.fullname = c.commenter instead of comment