115 lines
2.9 KiB
Markdown
115 lines
2.9 KiB
Markdown
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# Corrections
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## 1. Les titulaires
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`holder` : table commune à tous les titulaires
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- identifiant unique (`id`)
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- type de titulaire (`type` = 'PERSON' ou 'COMPANY')
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- date de création
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```sql
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create table holder (
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id bigint primary key generated always as identity,
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type text not null check (type in ('PERSON', 'COMPANY')),
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created_at timestamp not null default now()
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);
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```
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`person` : informations propres aux personnes physiques
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- prénom, nom, date de naissance
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```sql
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create table person (
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id bigint primary key references holder(id) on delete cascade,
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firstname text not null,
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lastname text not null,
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birthdate date not null
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);
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```
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`company` : informations propres aux entreprises
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- raison sociale, numéro d’immatriculation, date de création
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```sql
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create table company (
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id bigint primary key references holder(id) on delete cascade,
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name text not null,
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registration_number text unique not null,
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created_at date not null
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);
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```
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### Tests d'insertion des données
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```sql
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-- Création d’un titulaire de type personne physique
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insert into holder(type) values ('PERSON') returning id;
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-- Utilisons l'id qui est retourné (1)
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insert into person(id, firstname, lastname, birthdate)
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values (1, 'Françoise', 'Zanetti', '1995-04-12');
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```
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```sql
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-- Création d’un titulaire de type entreprise
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insert into holder(type) values ('COMPANY') returning id;
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-- Utilisons l'id qui est retourné (2)
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insert into company(id, name, registration_number, created_at)
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values (2, 'Boulangerie de Valorgue', 'FR19803269968', '2014-08-19');
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```
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### Vérification
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```sql
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select h.id, h.type, h.created_at,
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p.firstname || ' ' || p.lastname as person,
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c.name as company
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from holder h
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left join person p on p.id = h.id
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left join company c on c.id = h.id
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order by h.id;
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```
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#### 1.5.1 Pourquoi séparer `person` et `company` ?
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Parce que leurs attributs diffèrent (nom/prénom vs raison sociale).
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Cela évite les colonnes inutiles et permet des contraintes spécifiques à chaque type.
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#### 1.5.2 Pourquoi ne pas tout mettre dans une seule table holder ?
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Cela forcerait la présence de nombreuses colonnes nulles. La séparation améliore la cohérence et la lisibilité du schéma.
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#### 1.5.3 Quelle contrainte empêche d’insérer une person sans holder ?
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La clé étrangère references holder(id) dans person.
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### 1.6 Contôle de l'âge
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Contrainte déclarative
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```sql
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alter table person
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add constraint chk_person_minimum_age
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check (birthdate <= current_date - interval '15 years');
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```
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Contrainte procédurale avec un trigger :
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```sql
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create or replace function check_person_age()
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returns trigger as $$
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begin
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if new.birthdate > current_date - interval '15 years' then
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raise exception 'Holder must be at least 15 years old';
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end if;
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return new;
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end;
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$$ language plpgsql;
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create trigger trg_check_person_age
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before insert or update on person
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for each row execute procedure check_person_age();
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```
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