If I understand what you're asking you want to find all records in the clients table that don't have a corresponding record in pays. Assuming the tables are related on ClientID, you could use this query:

SELECT * ;
   FROM clients ;
   WHERE clients.ClientID NOT IN (SELECT ClientID FROM pays)

>Hi all,
>
>I have two tables, both are relationed.One of this have Clients and the other Pays of each client.The relation is (One-To-Many).The question is how can I know about those clients that have not pay.In other words all those records that have not any movement in the Client´s table.I want to extract those records in a query list.
>
>TIA