Le meilleur endroit pour faire respecter l'intégrité des données est la base de données. Soyez assuré que certains développeurs, intentionnellement ou non, trouveront un moyen d'introduire des éléments incohérents dans la base de données si vous les autorisez !
Voici un exemple avec des contraintes de vérification :
CREATE FUNCTION dbo.SignupMismatches()
RETURNS int
AS BEGIN RETURN (
SELECT count(*)
FROM Shift s
LEFT JOIN EventVolunteer ev
ON ev.EventId = s.EventId
AND ev.VolunteerId = s.VolunteerId
WHERE ev.Id is null
) END
go
ALTER TABLE Shift ADD CONSTRAINT chkSignup CHECK (dbo.SignupMismatches() = 0);
go
CREATE FUNCTION dbo.OverlapMismatches()
RETURNS int
AS BEGIN RETURN (
SELECT count(*)
FROM Shift a
JOIN Shift b
ON a.id <> b.id
AND a.Start < b.[End]
AND a.[End] > b.Start
AND a.VolunteerId = b.VolunteerId
) END
go
ALTER TABLE Shift ADD CONSTRAINT chkOverlap CHECK (dbo.OverlapMismatches() = 0);
Voici quelques tests pour les nouveaux contrôles d'intégrité des données :
insert into Volunteer (name) values ('Dubya')
insert into Event (name) values ('Build Wall Around Texas')
-- Dubya tries to build a wall, but Fails because he's not signed up
insert into Shift (VolunteerID, EventID, Description, Start, [End])
values (1, 1, 'Dunbya Builds Wall', '2010-01-01', '2010-01-02')
-- Properly signed up? Good
insert into EventVolunteer (VolunteerID, EventID)
values (1, 1)
insert into Shift (VolunteerID, EventID, Description, Start, [End])
values (1, 1, 'Dunbya Builds Wall', '2010-01-01', '2010-01-03')
-- Fails, you can't start the 2nd wall before you finished the 1st
insert into Shift (VolunteerID, EventID, Description, Start, [End])
values (1, 1, 'Dunbya Builds Second Wall', '2010-01-02', '2010-01-03')
Voici les définitions des tables :
set nocount on
if OBJECT_ID('Shift') is not null
drop table Shift
if OBJECT_ID('EventVolunteer') is not null
drop table EventVolunteer
if OBJECT_ID('Volunteer') is not null
drop table Volunteer
if OBJECT_ID('Event') is not null
drop table Event
if OBJECT_ID('SignupMismatches') is not null
drop function SignupMismatches
if OBJECT_ID('OverlapMismatches') is not null
drop function OverlapMismatches
create table Volunteer (
id int identity primary key
, name varchar(50)
)
create table Event (
Id int identity primary key
, name varchar(50)
)
create table Shift (
Id int identity primary key
, VolunteerId int foreign key references Volunteer(id)
, EventId int foreign key references Event(id)
, Description varchar(250)
, Start datetime
, [End] datetime
)
create table EventVolunteer (
Id int identity primary key
, VolunteerId int foreign key references Volunteer(id)
, EventId int foreign key references Event(id)
, Location varchar(250)
, [Day] datetime
, Description varchar(250)
)
