several key values in one field?

[Lingua2001]

Hi,

while trying to handle severl key values,
I wonder if it is more efficient to put
those values in a row seperated by a
certain seperator (eg. comma).

The talbe has two fields and looks like;

UID ForeinID
1     2,3,4,6
2    7,9,4,5
3    3,4
4    1,5,7,9
5    2,3,4,5

and the values of ForeignID is primary keys
of another table.

What would be the best way to handle this kind of
case (i.e. M-to-M relationship) in MySQL?

Thanks in advance.

Lingua