and now if I have the following table:

table contrat
(numsal number(4),
numcontrat number(5),
datedeb date,
dateend date
);

example :
numsal numcontrat datedeb    dateend
1           1     02/02/2008 10/03/2008
1           2     20/03/2008 30/04/2008
1           3     10/02/2008 15/04/2008
1           4     16/04/2008 15/05/2008
1           5     16/05/2008 31/08/2008
1           6     01/10/2008 31/10/2008
1           7     10/11/2008 31/12/2008
1           8     10/11/2008 15/12/2008

numcontrat no3 overlap no1 and no2
numcontrat no4 overlap no2 
numcontrat no8 overlap no7

what is the script that can give me this?

numsal  numcontrat  overlap contrats
1       3                   1
        3                   2

1       4                   2

1       8                   7

etc...