I have this code, how to update in sql?

Question

have tried

$sql = " UPDATE biblioteca SET nome_usuario WHERE nome_usuario IN ( SELECT nome_usuario FROM ( SELECT  nome_usuario, COUNT(id_usuario) FROM orders WHERE nome_usuario )"

---

$sql = "UPDATE usuario(nome_usuario) VALUES ('$name') WHERE nome_usuario=".$_REQUEST["nome_usuario"];

---

$sql = "UPDATE usuario(nome_usuario) VALUES ('$name') WHERE nome_usuario= '$name'";

---

<?php
    switch($_REQUEST["acao"]){
        case "editar":

            $sql = " UPDATE biblioteca SET nome_usuario WHERE nome_usuario IN ( SELECT nome_usuario FROM ( SELECT  nome_usuario, COUNT(id_usuario) FROM orders WHERE nome_usuario )"

             // SELECT * FROM biblioteca 
             // WHERE id_biblioteca=".$_REQUEST["id_biblioteca"];

            # $sql = "UPDATE usuario(nome_usuario) VALUES ('$name') WHERE nome_usuario= '$name'";
            # $sql = "UPDATE usuario(nome_usuario) VALUES ('$name') WHERE nome_usuario=".$_REQUEST["nome_usuario"];
            $res = $conn->query($sql);
            if($res==true){
                print "<br><div class='alert alert-success'>Usuário atualizado com sucesso!</div>";
            }else{
                print "<div class='alert alert-danger'>Não é possível atualizar o usuário.</div>";
            }
        break;
    }
?>

Answer 1

From what I understand you want to update a user’s name, if that’s what I believe the code below can solve:

<?php

$id = $_POST['id'];
$name = $_POST['name'];


$sql = "UPDATE users
SET name = '{$name}'
WHERE id = {$id}";

$res = $conn->query($sql);

Now if you want to update the user who is registered in the library table, you have to make a relationship between the library table and the users table.

If you want to register a user in the table library it would be ideal to have a column called user_id (foreign key) that refers to the id of the table of users.