# Referensi Cepat PostgreSQL

*Tabel, query, join, index, JSON, dan role*

> Source: PostgreSQL Documentation (postgresql.org/docs) · MIT

## Menghubungkan

### Command Line

```
psql -U postgres
psql -h localhost -p 5432 -U user -d mydb
psql "postgresql://user:pass@host:5432/mydb"
```

### Meta-Command psql

| Command | Description |
|---------|-------------|
| `\l` | Daftar database |
| `\c dbname` | Hubungkan ke database |
| `\dt` | Daftar tabel |
| `\d tablename` | Tampilkan struktur tabel |
| `\dn` | Daftar schema |
| `\du` | Daftar role |
| `\q` | Keluar dari psql |
| `\i file.sql` | Jalankan file SQL |

## Tabel & Schema

### Buat Tabel

```
CREATE TABLE users (
  id SERIAL PRIMARY KEY,
  name VARCHAR(100) NOT NULL,
  email TEXT UNIQUE,
  created_at TIMESTAMPTZ DEFAULT NOW()
);
```

### Operasi Schema

```
CREATE SCHEMA app;
CREATE TABLE app.users (id SERIAL PRIMARY KEY);
SET search_path TO app, public;
DROP SCHEMA app CASCADE;
```

### Alter Table

```
ALTER TABLE users ADD COLUMN age INT;
ALTER TABLE users ALTER COLUMN name TYPE TEXT;
ALTER TABLE users DROP COLUMN age;
ALTER TABLE users RENAME TO customers;
```

## Tipe Data

### Numerik

| Command | Description |
|---------|-------------|
| `INTEGER / INT` | Integer 4-byte |
| `BIGINT` | Integer 8-byte |
| `SERIAL` | Integer auto-increment |
| `NUMERIC(p,s)` | Numerik eksak (mis. NUMERIC(10,2)) |
| `REAL / DOUBLE PRECISION` | Floating-point (4 / 8 byte) |
| `BOOLEAN` | true / false / null |

### String & Biner

| Command | Description |
|---------|-------------|
| `TEXT` | Teks panjang tak terbatas |
| `VARCHAR(n)` | Teks variabel hingga n karakter |
| `CHAR(n)` | Teks panjang tetap |
| `BYTEA` | Data biner |
| `UUID` | ID unik universal 128-bit |

### Tanggal, JSON & Array

| Command | Description |
|---------|-------------|
| `DATE` | Tanggal kalender |
| `TIMESTAMPTZ` | Timestamp dengan zona waktu |
| `INTERVAL` | Rentang waktu (mis. '2 days') |
| `JSONB` | JSON biner (dapat diindeks) |
| `INT[] / TEXT[]` | Tipe array |

## Query

### Insert

```
INSERT INTO users (name, email)
VALUES ('Alice', 'alice@example.com')
RETURNING id;

INSERT INTO users (name, email) VALUES
('Bob', 'bob@ex.com'),
('Carol', 'carol@ex.com');
```

### Select

```
SELECT * FROM users WHERE id = 1;
SELECT name, email FROM users
ORDER BY name LIMIT 10 OFFSET 20;
```

### Update

```
UPDATE users SET email = 'new@ex.com'
WHERE id = 1 RETURNING *;
```

### Upsert

```
INSERT INTO users (email, name)
VALUES ('a@ex.com', 'Alice')
ON CONFLICT (email) DO UPDATE
SET name = EXCLUDED.name;
```

### Delete

```
DELETE FROM users WHERE id = 1 RETURNING *;
TRUNCATE TABLE users RESTART IDENTITY;
```

## Join & Subquery

### Tipe Join

| Command | Description |
|---------|-------------|
| `INNER JOIN` | Baris yang cocok di kedua tabel |
| `LEFT JOIN` | Semua baris kiri + yang cocok di kanan |
| `RIGHT JOIN` | Semua baris kanan + yang cocok di kiri |
| `FULL OUTER JOIN` | Semua baris dari kedua tabel |
| `CROSS JOIN` | Produk kartesian |
| `LATERAL JOIN` | Subquery yang mereferensikan baris luar |

### CTE (Common Table Expression)

```
WITH active AS (
  SELECT * FROM users WHERE active = true
)
SELECT a.name, o.total
FROM active a
JOIN orders o ON a.id = o.user_id;
```

### Subquery

```
SELECT name FROM users
WHERE id IN (
  SELECT user_id FROM orders
  WHERE total > 100
);
```

## Index

### Buat & Hapus

```
CREATE INDEX idx_name ON users(name);
CREATE UNIQUE INDEX idx_email ON users(email);
CREATE INDEX idx_gin ON posts USING GIN(tags);
DROP INDEX idx_name;
```

### Tipe Index

| Command | Description |
|---------|-------------|
| `B-tree` | Default, cocok untuk =, <, >, BETWEEN |
| `Hash` | Hanya perbandingan kesamaan |
| `GIN` | Generalized inverted — array, JSONB, full-text |
| `GiST` | Generalized search — geometri, range |
| `BRIN` | Block range — tabel besar yang terurut |

### Analisis Query

```
EXPLAIN ANALYZE
SELECT * FROM users WHERE name = 'Alice';
```

## Fungsi & Prosedur

### Fungsi SQL

```
CREATE FUNCTION active_count()
RETURNS INTEGER AS $$
  SELECT COUNT(*)::INT FROM users
  WHERE active = true;
$$ LANGUAGE sql;
SELECT active_count();
```

### Fungsi PL/pgSQL

```
CREATE FUNCTION greet(name TEXT)
RETURNS TEXT AS $$
BEGIN
  RETURN 'Hello, ' || name;
END;
$$ LANGUAGE plpgsql;
```

### Fungsi Bawaan Berguna

| Command | Description |
|---------|-------------|
| `NOW() / CURRENT_TIMESTAMP` | Timestamp saat ini dengan TZ |
| `AGE(ts1, ts2)` | Interval antara dua timestamp |
| `COALESCE(a, b)` | Nilai non-null pertama |
| `NULLIF(a, b)` | NULL jika a = b |
| `GENERATE_SERIES(1,10)` | Hasilkan baris nilai berurutan |
| `STRING_AGG(col, ',')` | Gabungkan nilai dengan separator |

## Role & Izin

### Manajemen Role

```
CREATE ROLE app LOGIN PASSWORD 'secret';
ALTER ROLE app SET search_path TO myapp;
DROP ROLE app;
```

### Grant

```
GRANT ALL ON DATABASE mydb TO app;
GRANT SELECT, INSERT ON users TO reader;
GRANT USAGE ON SCHEMA public TO app;
REVOKE INSERT ON users FROM reader;
```

### Row-Level Security

```
ALTER TABLE users ENABLE ROW LEVEL SECURITY;
CREATE POLICY user_own ON users
FOR ALL USING (id = current_setting('app.uid')::INT);
```

## Dukungan JSON

### Operator JSONB

| Command | Description |
|---------|-------------|
| `->'key'` | Ambil nilai JSON berdasarkan key (sebagai JSON) |
| `->>'key'` | Ambil nilai JSON berdasarkan key (sebagai teks) |
| `#>'{a,b}'` | Ambil nilai bersarang berdasarkan path |
| `@>` | Mengandung (kiri mencakup kanan) |
| `?` | Key ada |
| `\|\|` | Gabungkan nilai JSONB |

### Query JSONB

```
SELECT data->>'name' FROM profiles
WHERE data @> '{"active": true}';

SELECT * FROM profiles
WHERE data ? 'email';
```

### Fungsi JSONB

```
SELECT jsonb_each(data) FROM profiles;
SELECT jsonb_array_elements('[1,2,3]');
SELECT jsonb_set(data, '{name}', '"Alice"')
FROM profiles WHERE id = 1;
```

## Pola Umum

### Transaksi

```
BEGIN;
UPDATE accounts SET balance = balance - 100
WHERE id = 1;
UPDATE accounts SET balance = balance + 100
WHERE id = 2;
COMMIT;  -- atau ROLLBACK;
```

### Window Function

```
SELECT name, salary,
  RANK() OVER (ORDER BY salary DESC),
  AVG(salary) OVER (PARTITION BY dept)
FROM employees;
```

### Salin Data

```
COPY users TO '/tmp/users.csv'
WITH (FORMAT csv, HEADER);
COPY users FROM '/tmp/users.csv'
WITH (FORMAT csv, HEADER);
```

### Backup pg_dump

```
pg_dump -U postgres mydb > backup.sql
pg_dump -Fc mydb > backup.dump
pg_restore -d mydb backup.dump
```