check with select - Mailing list pgsql-sql

From edouard.boucher@free.fr
Subject check with select
Date
Msg-id 20030515122001.GA7851@comploteur.gibbonie.creolie
Whole thread Raw
Responses Re: check with select
List pgsql-sql
Hi,

I have a table referancing services of a company :
CREATE TABLE Services (      id INTEGER NOT NULL PRIMARY KEY,      nom VARCHAR(30) NOT NULL -- name of the service
);

each of them can have many workers and many boss
but at least 1 boss

So i have a table referancing workers and boss :

CREATE TABLE EmployesDsServices (      service INTEGER REFERENCES Services (id)                  ON DELETE CASCADE
DEFERRABLEINITIALLY DEFERRED,      employe INTEGER REFERENCES Employes (id)       ON DELETE CASCADE DEFERRABLE
INITIALLYDEFERRED,      niveau CHAR(1), -- R -> boss, S -> worker      CONSTRAINT niveau_valide CHECK (NIVEAU IN
('R','S')),     PRIMARY KEY (service, employe)
 
);

to check that at any time a service always have at least one boss,
i would like :

CREATE ASSERTION chaque_service_a_au_moins_un_responsable CHECK      (NOT EXISTS (SELECT id FROM Services LEFT OUTER
JOIN       (SELECT * FROM employesdsservices WHERE niveau='R') AS resp ON      id=service GROUP BY id HAVING
COUNT(niveau)<1));

the problem is that this is not valid in postgreSQL,
so i tryed to use a trigger, but it seems that it is not possible to
make a trigger deferrable (as the 2 tables are mutualy dependent).

i would like something i can use like this :

begin;
insert into services ...
insert into employesdsservices ...
end;

is there a way to do this, a check after each insert, update, delete in
both tables?

i know my constraint is anyway very slow, but this is for a scolar
project about theory and performance realy dont matters.

thank you for help

Edouard Boucher


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