# Implémentation du modèle

## 1. Les titulaires (holder)

```sql
create type holder_type
  as enum ('BANK', 'PERSON', 'COMPANY');
```

Création de la table `holder`. C'est une table commune à tous les titulaires qu'ils soient des individus ou des sociétés. Elle sert à donner un identifiant unique et défini le type de titulaire.

```sql
create table holder (
  "id" bigint primary key generated always as identity,
  "type" holder_type not null,
  "created_at" timestamp not null default current_timestamp
);
```

- `bigint` : entier sur 64 bits
- `primary key` : clé primaire, identification unique de l'enregristrement
- `generated always as identity` : incrémentation automatique (1, 2, 3, 4, ...)
- `not null` : Il est obligatoire de spécifier une valeur.
- Le type est forcé aux 3 valeurs de l'énumération `holder_type`
- `current_timestamp` date **et** heure courante. Version moderne de `now()`

### 1.1 Les individus (person)

Création de la table `person`.

```sql
create table person (
  "id" bigint primary key references holder(id) on delete cascade,
  "firstname" text not null,
  "lastname" text not null,
  "birthdate" date not null check (birthdate <= current_date - interval '15 years')
);
```

### 1.2 les sociétés (company)

```sql
create table company (
  "id" bigint primary key references holder(id) on delete cascade,
  "name" text not null,
  "registration_number" text unique not null,
  "creation_date" date not null
);
```

### 1.3 La banque (bank)

```sql
create table bank (
  "id" bigint primary key references holder(id),
  "name" text
);
```

## 2. Les monnaies

```sql
create table currency (
  "code" text primary key
);
```

```sql
create table exchange_rate (
  "currency_code" text references currency(code) on delete cascade,
  "date" date ,
  "rate" decimal not null,
  primary key (currency_code, date)
);
```

## 3. Les comptes

```sql
create table account (
  "id" bigint primary key generated always as identity,
  "opened_at" date not null default current_date,
  "balance" numeric(18,6) not null default 0,
  "currency_code" text not null references currency (code)
);
```

```sql
create table account_holder (
  "account_id" int not null references account(id) on delete cascade,
  "holder_id" int not null references holder(id) on delete cascade,
  "share" decimal(4,3) not null default 1 check (share > 0 and share <= 1),
  primary key (account_id, holder_id)
);
```

### 4. Les transactions

```sql
create table transaction (
  "id" bigint primary key generated always as identity,
  "transaction_date" timestamp not null default current_timestamp,
  amount decimal not null check (amount > 0)
);
```

```sql
create table operation (
  "id" bigint primary key generated always as identity,
  "transaction_id" bigint not null references transaction(id),
  "account_id" bigint not null references account(id),
  amount decimal not null check (amount > 0),
  direction text not null check (direction in ('DEBIT', 'CREDIT'))
);
```