Piye carane model lan ORM bisa ngerjani?

Question

Accepted Answer

A **model** yaiku kelas Python sing nemtokake struktur data mu — saben model pemetaa menyang tabel database, lan saben atribut pemetaa menyang kolom. **ORM (Object-Relational Mapper)** ngidini mu komunikasi karo database nggunakake obyek lan metode Python tinimbang nulis SQL mentah.

## Nemtokake model

```python
from django.db import models

class Article(models.Model):
    title = models.CharField(max_length=200)       # → VARCHAR column
    body = models.TextField()                        # → TEXT column
    published = models.BooleanField(default=False)
    created_at = models.DateTimeField(auto_now_add=True)  # set on creation
    views = models.IntegerField(default=0)

def __str__(self):
        return self.title                            # readable representation (admin, shell)
```

Saben kolom model pemetaa menyang kolom database sing duwe tipe sing cocok. Nglakokake migrasi nggawe tabel sing cocok — sampeyan ora ngriting `CREATE TABLE` dhewe.

## CRUD karo ORM (tanpa SQL)

```python
# CREATE
article = Article.objects.create(title="Hello", body="...")

# READ — query with Python methods
Article.objects.all()                            # all rows → SELECT *
Article.objects.get(id=1)                         # one row by primary key
Article.objects.filter(published=True)            # WHERE published = true
Article.objects.filter(title__icontains="django") # WHERE title ILIKE '%django%'
Article.objects.exclude(views=0).order_by("-created_at")  # complex queries, chained

# UPDATE
article.title = "Updated"
article.save()
Article.objects.filter(published=False).update(published=True)  # bulk update

# DELETE
article.delete()
```

ORM nerjemahake panggilan Python iki menyang SQL kanthi otomatis. Pamadhegan kolom (`__icontains`, `__gte`, `__in`, lsp.) ngandhakake kondisi WHERE kanthi cara Python.

## Kenapa ORM? Kauntungan lan trade-off

```text
✓ Write database code in Python — no SQL, more readable, less error-prone
✓ Database-agnostic — the same code works on PostgreSQL, MySQL, SQLite
✓ SECURITY — parameterized queries by default → prevents SQL injection
✓ Integrates with migrations, admin, forms (define the model once)
⚠️ Trade-off: can generate inefficient queries (e.g. N+1) if used carelessly —
   sometimes you need select_related/prefetch_related or raw SQL for complex cases
```

## Model minangka satunggal sumber kabenaran (DRY)

```text
One model definition drives: the database schema (migrations), the admin interface,
ModelForms, and serializers (DRF) — define it once, reuse everywhere.
```

## Kenapa iki penting

Model lan ORM minangka pusat Django — iki carane sampeyan nemtokake lan ngerjani data aplikasi mu, sing minangka jantung saka akeh aplikasi web.

Pamahaman wong iki penting saben dina: model nemtokake struktur data mu (pemetaan kelas menyang tabel, atribut menyang kolom) lan dadi **satunggal sumber kabenaran** sing nguruski skema database, antarmuka admin, formulir, lan serilaizer API (filosofi DRY).

ORM ngidini mu nulis operasi database ing **Python sing resik lan gampang karo basa**, duwe kauntungan gedhe: portabilitas database (kode sing padha padha mlayu ing database beda), integrasi rapet karo Django liyane, lan penting banget **keamanan** (nggunakake parameterized query kanthi standar, nyegah SQL injection).

Ngerti carane nemtokake model karo kolom sing cocok, nglakokake operasi CRUD, lan manggal nggunakake sintaks pamadhegan ORM minangka pangalaman dasar kanggo nggawe aplikasi Django.

Tolak patuwas penting yaiku kamanungsan ORM **trade-off** — yen manggal sing gampang bisa dadi ora efisien (masalah N+1) tanpa ati — sing ngarahake teknike optimisasi.

Larik model/ORM yaiku ngendi aplikasi Django mbuwang akeh logika kuwi, nggawe iku pusat, bahan sing kudu dikuasai.