thanks for your answers, but they don't answer to the questions.
On first point, the LEFT(postcode, 2) works for french postcode which are meanful on the first 2 digits, but not for UK for eg which is meanfull on the first 3 digits. My question is more generally : can I create restrictions with wildcard caracters (for eg on a customer field, make a security restriction '*SAMSUNG*') ?
On the second point, I suppose your proposition of 2 lines in Section Access looks like :
line 1 : COUNTRY = UK, CITY = BLANK
line 2 : COUNTRY = FR, CITY = PARIS
The result of this restriction is COUNTRY = UK, FR and CITY = PARIS
So, I would only see PARIS, and none of the UK cities, while my need would be to see all UK cities + Paris.
More generally, on the second point, my question is : is it possible to perform restrictions with the OR operator between the lines, instead of AND.
In the above example, the restriction do not work because the restriction makes an AND for the 2 lines of restriction : (COUNTRY = UK) AND (COUNTRY = FR AND CITY = PARIS).
While my need is to get the result with an OR operator : (COUNTRY = UK) OR (COUNTRY = FR AND CITY = PARIS)