“Relation Query Language” tutorial

Let’s discover RQL with examples.

Schema

We will assume the following data model.

Person:

name      varchar(64) NOT NULL
firstname varchar(64)
sex       char(1) DEFAULT 'M'
title     varchar(128)
email     varchar(128)
web       varchar(128)
tel       integer
birthdate date

Company:

name  varchar(64)
web   varchar(128)
tel   varchar(15)
adr   varchar(128)
cp    varchar(12)
city  varchar(32)

Workcase:

title varchar(128)
ref   varchar(12)

Comment:

diem date
type char(1)
para varchar(512)

with relationships:

Person works_for Company
Person commented_by Comment
Company commented_by Comment
Person concerned_by Workcase
Company concerned_by Workcase

Toutes les entités ont un attribut supplémentaire ‘eid’, permettant d’identifier chaque instance de manière unique.

De plus si les métadonnées sont utilisées, vous disposez pour chaque type d’entité des relations “creation_date”, “modification_date” dont l’objet est une entité de type Dates (il y a un “s” pour ne pas avoir de conflit avec le type de base “date”), ainsi que de la relation “owned_by” dont l’objet est une entité de type Euser. Les schemas standards de ces types d’entités sont les suivants :

Dates:

day date

Euser:

login     varchar(64) not null
firstname varchar(64)
surname   varchar(64)
password  password
role      choice('admin','user','anonymous') default 'user'
email     varchar(128)
web       varchar(128)
birthday  date

Enfin, il existe la relation spéciale “is” permettant de spécifier le type d’une variable.

Essentials

1. Alls persons

   Person X ;
   or
   Any X WHERE X is Person ;
   

2. The company namend Logilab

   Company S WHERE S name 'Logilab' ;
   

3. All entities with a name starting with ‘Log’

   Any S WHERE S name LIKE 'Log%' ;
   or
   Any S WHERE S name ~= 'Log%' ;
   

   This query can return entities of type Person and Company.

4. All persons working for a company named Logilab

   Person P WHERE P works_for S, S name "Logilab" ;
   or
   Person P WHERE P works_for S AND S name "Logilab" ;
   or
   Person P WHERE P works_for "Logilab" ;
   

   La dernière forme fonctionne car “nom” est le premier attribut des entités de type “Société” XXX nico: toujours vrai ?

5. Companies named Caesium or Logilab

   Company S WHERE S name IN ('Logilab','Caesium') ;
   or
   Company S WHERE S name 'Logilab' OR S name 'Caesium' ;
   

6. All companies that are not named Caesium or Logilab

   Company S WHERE NOT S name IN ('Logilab','Caesium') ;
   or
   Company S WHERE NOT S name 'Logilab' AND NOT S name 'Caesium' ;
   

7. All entities commented by the entity number 43

   Any X WHERE X commented_by N, N eid 43 ;
   

8. All persons sorted by birth date in descending order

   Any X WHERE X is Person, X birthdate D ORDERBY D DESC ;
   

9. All persons grouped by company

   Person X WHERE X works_for S GROUPBY S,X ;
   

   On note qu’il faut définir une variable pour s’en servir pour le groupage. De plus les variables séléctionnées doivent être groupées (mais les variables groupées ne doivent pas forcément être sélectionnées).

XXX nico: c’est peu utile comme requête

Exemples avancés

1. All persons that have an empty name (i.e NULL)

   Person P WHERE P name NULL ;
   

2. All persons that do not work for a company

   Person P WHERE NOT P works_for S ;
   

3. All the companies that the person named ‘toto’ does not work for

   Company S WHERE NOT P works_for S , P name 'toto' ;
   or
   Company S WHERE NOT 'toto' works_for S ;
   

4. All the entities modified yesterday and today

   Any X WHERE X modification_date <= today, X modification_date >= today - 1
   

5. All the comments without type that required action within 7 days, sorted by date

   Any N, D where N is Comment, N type NULL, N diem D, N diem >= today,
   N diem < today + 7 ORDERBY D
   

6. All persons that have homonyms (each name listed only once)

   Person X,Y where X name NX, Y name NX, X eid XE, Y eid > XE