Query Builder - Knowledge of Laravel

Cos’è il Query Builder

Il Query Builder di Laravel offre un’interfaccia fluida per costruire ed eseguire query sul database. Parte da DB::table() e concatena i metodi.

use Illuminate\Support\Facades\DB;

$users = DB::table('users')->get();

Internamente usa il parameter binding di PDO, quindi la protezione da SQL injection è automatica.

Il Query Builder funziona su tutti i database supportati (MySQL, MariaDB, PostgreSQL, SQLite, SQL Server). Il codice non cambia cambiando database.

Quando usare il Query Builder o Eloquent

Situazione	Consigliato
Servono modelli e relazioni	Eloquent
Aggregazioni e report complessi	Query Builder
Prestazioni su grandi volumi	Query Builder
Operazioni semplici su tabelle esistenti	Query Builder
Migration e seeder	Query Builder

Recupero dei dati

Tutti i record

$users = DB::table('users')->get();

foreach ($users as $user) {
    echo $user->name;
}

get() restituisce Illuminate\Support\Collection. Ogni record è uno stdClass.

Un solo record

$user = DB::table('users')->where('name', 'Mario Rossi')->first();
$user = DB::table('users')->where('name', 'Mario Rossi')->firstOrFail();
$email = DB::table('users')->where('name', 'Mario Rossi')->value('email');
$user = DB::table('users')->find(3);

Elenchi di colonne

$emails = DB::table('users')->pluck('email');
$emailByName = DB::table('users')->pluck('email', 'name');

Elaborazione a blocchi

use Illuminate\Support\Collection;

DB::table('users')->orderBy('id')->chunk(100, function (Collection $users) {
    foreach ($users as $user) {
        // ...
    }
});

DB::table('users')->where('active', false)
    ->chunkById(100, function (Collection $users) {
        foreach ($users as $user) {
            DB::table('users')
                ->where('id', $user->id)
                ->update(['active' => true]);
        }
    });

Se aggiorni/elimini record mentre esegui chunk, usa chunkById() per evitare disallineamenti.

Streaming (LazyCollection)

DB::table('users')->orderBy('id')->lazy()->each(function (object $user) {
    // Un utente alla volta
});

Aggregazioni

$count   = DB::table('users')->count();
$maxAge  = DB::table('users')->max('age');
$minAge  = DB::table('users')->min('age');
$avgAge  = DB::table('users')->avg('age');
$total   = DB::table('orders')->sum('amount');

$avgPremium = DB::table('orders')
    ->where('plan', 'premium')
    ->avg('amount');

Verifica esistenza

if (DB::table('orders')->where('finalized', 1)->exists()) {
    // Esiste
}

if (DB::table('orders')->where('finalized', 1)->doesntExist()) {
    // Non esiste
}

SELECT

$users = DB::table('users')
    ->select('name', 'email as user_email')
    ->get();

$users = DB::table('users')->distinct()->get();

$query = DB::table('users')->select('name');
$users = $query->addSelect('age')->get();

WHERE

Condizioni base

$users = DB::table('users')->where('votes', 100)->get();
$users = DB::table('users')->where('votes', '>=', 100)->get();
$users = DB::table('users')->where('name', 'like', 'Mario%')->get();

$users = DB::table('users')
    ->where('status', 'active')
    ->where('age', '>', 20)
    ->get();

$users = DB::table('users')
    ->where('votes', '>', 100)
    ->orWhere('name', 'Mario Rossi')
    ->get();

Raggruppamento

use Illuminate\Database\Query\Builder;

$users = DB::table('users')
    ->where('active', true)
    ->where(function (Builder $query) {
        $query->where('role', 'admin')
              ->orWhere('role', 'moderator');
    })
    ->get();
// WHERE active = 1 AND (role = 'admin' OR role = 'moderator')

whereIn / whereBetween / whereNull

$users = DB::table('users')->whereIn('id', [1, 2, 3])->get();
$users = DB::table('users')->whereNotIn('id', [1, 2, 3])->get();

$users = DB::table('users')->whereBetween('age', [20, 40])->get();

$users = DB::table('users')->whereNull('deleted_at')->get();
$users = DB::table('users')->whereNotNull('email_verified_at')->get();

whereLike

$users = DB::table('users')
    ->whereLike('name', '%Rossi%')
    ->get();

$users = DB::table('users')
    ->whereLike('name', '%Rossi%', caseSensitive: true)
    ->get();

whereAny / whereAll

$users = DB::table('users')
    ->where('active', true)
    ->whereAny(['name', 'email', 'bio'], 'like', '%Laravel%')
    ->get();

$posts = DB::table('posts')
    ->whereAll(['title', 'content'], 'like', '%Laravel%')
    ->get();

whereNullSafeEquals

whereNullSafeEquals (e orWhereNullSafeEquals) confronta considerando due NULL come uguali. L’operatore = normale rende NULL = NULL come false; con whereNullSafeEquals invece i NULL sono uguali. Corrisponde a <=> di MySQL e IS NOT DISTINCT FROM di PostgreSQL.

$lastLoginIp = $request->input('last_login_ip');

$users = DB::table('users')
    ->whereNullSafeEquals('last_login_ip', $lastLoginIp)
    ->get();

Il classico where('column', null) diventa WHERE column IS NULL; whereNullSafeEquals('column', $value) funziona in modo coerente anche quando il valore associato è o non è null. Molto utile con input utente potenzialmente nullo.

JOIN

$users = DB::table('users')
    ->join('orders', 'users.id', '=', 'orders.user_id')
    ->select('users.name', 'orders.amount')
    ->get();

$users = DB::table('users')
    ->leftJoin('orders', 'users.id', '=', 'orders.user_id')
    ->get();

$users = DB::table('users')
    ->join('contacts', 'users.id', '=', 'contacts.user_id')
    ->join('orders', 'users.id', '=', 'orders.user_id')
    ->select('users.*', 'contacts.phone', 'orders.amount')
    ->get();

JOIN con sottoquery

$latestOrders = DB::table('orders')
    ->select('user_id', DB::raw('MAX(created_at) as last_order_at'))
    ->groupBy('user_id');

$users = DB::table('users')
    ->joinSub($latestOrders, 'latest_orders', function ($join) {
        $join->on('users.id', '=', 'latest_orders.user_id');
    })
    ->get();

Ordinamento, raggruppamento, limit

$users = DB::table('users')->orderBy('name', 'asc')->get();

$users = DB::table('users')
    ->orderBy('last_name')
    ->orderBy('first_name', 'desc')
    ->get();

$users = DB::table('users')->inRandomOrder()->get();

$orders = DB::table('orders')
    ->select('status', DB::raw('COUNT(*) as count'))
    ->groupBy('status')
    ->get();

$orders = DB::table('orders')
    ->select('user_id', DB::raw('SUM(amount) as total'))
    ->groupBy('user_id')
    ->having('total', '>', 10000)
    ->get();

$users = DB::table('users')
    ->skip(10)
    ->take(5)
    ->get();

Sottoquery

$activeUsers = DB::table('users')->select('id')->where('is_active', 1);

$comments = DB::table('comments')
    ->whereIn('user_id', $activeUsers)
    ->get();

$users = DB::table('users')
    ->select('name')
    ->selectSub(function ($query) {
        $query->from('orders')
              ->selectRaw('COUNT(*)')
              ->whereColumn('orders.user_id', 'users.id');
    }, 'order_count')
    ->get();

Espressioni Raw

Le espressioni Raw vengono inserite come SQL. Passare input utente direttamente causa SQL injection. Usa sempre binding.

$users = DB::table('users')
    ->select(DB::raw('count(*) as user_count, status'))
    ->groupBy('status')
    ->get();

$orders = DB::table('orders')
    ->selectRaw('price * ? as price_with_tax', [1.10])
    ->get();

$orders = DB::table('orders')
    ->whereRaw('price > IF(state = "IT", ?, 100)', [500])
    ->get();

$orders = DB::table('orders')
    ->select('department', DB::raw('SUM(amount) as total'))
    ->groupBy('department')
    ->havingRaw('SUM(amount) > ?', [100000])
    ->get();

$orders = DB::table('orders')
    ->orderByRaw('updated_at - created_at DESC')
    ->get();

INSERT / UPDATE / DELETE

INSERT

DB::table('users')->insert([
    'email' => 'mario@example.com',
    'name'  => 'Mario Rossi',
]);

DB::table('users')->insert([
    ['email' => 'mario@example.com', 'name' => 'Mario Rossi'],
    ['email' => 'giulia@example.com', 'name' => 'Giulia Bianchi'],
]);

$id = DB::table('users')->insertGetId([
    'email' => 'luca@example.com',
    'name'  => 'Luca Verdi',
]);

UPSERT

DB::table('users')->upsert(
    [
        ['email' => 'mario@example.com', 'name' => 'Mario Rossi', 'votes' => 5],
        ['email' => 'giulia@example.com', 'name' => 'Giulia Bianchi', 'votes' => 10],
    ],
    uniqueBy: ['email'],
    update: ['name', 'votes']
);

UPDATE

$affected = DB::table('users')
    ->where('id', 1)
    ->update(['name' => 'Mario R.', 'updated_at' => now()]);

DB::table('users')->where('id', 1)->increment('votes');
DB::table('users')->where('id', 1)->increment('votes', 5);
DB::table('users')->where('id', 1)->decrement('votes');
DB::table('users')->where('id', 1)->decrement('balance', 100);

DELETE

$deleted = DB::table('users')->where('status', 'inactive')->delete();

DB::table('users')->truncate();

Query condizionali (when)

$status = request('status');
$sortBy = request('sort', 'name');

$users = DB::table('users')
    ->when($status, function ($query, $status) {
        $query->where('status', $status);
    })
    ->when($sortBy === 'email', function ($query) {
        $query->orderBy('email');
    }, function ($query) {
        $query->orderBy('name');
    })
    ->get();

Debug

$sql = DB::table('users')->where('active', true)->toSql();
$bindings = DB::table('users')->where('active', true)->getBindings();

DB::table('users')->where('active', true)->dump();
DB::table('users')->where('active', true)->dd();

dd() è comodo in debug ma non usarlo in produzione. toSql() e getBindings() sono più sicuri.

Riepilogo

Metodi più usati

Metodo	Descrizione
`get()`	Tutti i record (Collection)
`first()`	Primo record
`find($id)`	Per ID
`value($column)`	Valore di una colonna
`pluck($column)`	Elenco valori di una colonna
`count()`	Conteggio
`sum($col)`	Somma
`avg($col)`	Media
`max($col)` / `min($col)`	Massimo/minimo
`exists()`	Verifica esistenza
`insert([...])`	Insert
`update([...])`	Update
`delete()`	Delete
`chunk($n, fn)`	A blocchi
`when($cond, fn)`	Condizionale
`toSql()`	Verifica SQL

Query Builder vs Eloquent

Il Query Builder è più a basso livello e restituisce stdClass. Se non ti servono relazioni ed eventi dei modelli è più semplice e veloce.

// Eloquent
$users = User::where('active', true)->get();
echo $users[0]->name; // Istanza User

// Query Builder
$users = DB::table('users')->where('active', true)->get();
echo $users[0]->name; // stdClass

​Cos’è il Query Builder

​Quando usare il Query Builder o Eloquent

​Recupero dei dati

​Tutti i record

​Un solo record

​Elenchi di colonne

​Elaborazione a blocchi

​Streaming (LazyCollection)

​Aggregazioni

​Verifica esistenza

​SELECT

​WHERE

​Condizioni base

​Raggruppamento

​whereIn / whereBetween / whereNull

​whereLike

​whereAny / whereAll

​whereNullSafeEquals

​JOIN

​JOIN con sottoquery

​Ordinamento, raggruppamento, limit

​Sottoquery

​Espressioni Raw

​INSERT / UPDATE / DELETE

​INSERT

​UPSERT

​UPDATE

​DELETE

​Query condizionali (when)

​Debug

​Riepilogo

Cos’è il Query Builder

Quando usare il Query Builder o Eloquent

Recupero dei dati

Tutti i record

Un solo record

Elenchi di colonne

Elaborazione a blocchi

Streaming (LazyCollection)

Aggregazioni

Verifica esistenza

SELECT

WHERE

Condizioni base

Raggruppamento

whereIn / whereBetween / whereNull

whereLike

whereAny / whereAll

whereNullSafeEquals

JOIN

JOIN con sottoquery

Ordinamento, raggruppamento, limit

Sottoquery

Espressioni Raw

INSERT / UPDATE / DELETE

INSERT

UPSERT

UPDATE

DELETE

Query condizionali (when)

Debug

Riepilogo