create table Client
(Client_id number, Address varchar2);

create table Jobs 
(Client_id number, Action_id number);

create table Action
(Action_id number, Priority number);

Insert into Client values (1, "1 Acacia Ave");
Insert into Client values (2, "7 High St");
Insert into Client values (3, "88 Pudding Lane");

Insert into Jobs values (1, 1);
Insert into Jobs values (1, 2);
Insert into Jobs values (1, 3);
Insert into Jobs values (2, 4);
Insert into Jobs values (2, 5);
Insert into Jobs values (2, 6);
Insert into Jobs values (3, 7);
Insert into Jobs values (3, 8);

Insert into Action values (1, 1);
Insert into Action values (2, 5);
Insert into Action values (3, 2);
Insert into Action values (4, 4);
Insert into Action values (5, 3);
Insert into Action values (6, 3);
Insert into Action values (7, 5);
Insert into Action values (8, 2);

Address		Priority
-------------	------------
1 Acacia Ave	1
88 Pudding Lane	2
7 High St	3 

select address, priority
from 
(select c.address, a.priority, row_number() over (partition by c.client_id order by priority) as rn
from
client c, jobs j, action a
where c.client_id = j.client_id
and j.action_id = a.action_id)
where rn=1
order by priority

SQL> select clt.address
  2  ,      min(acn.priority)
  3  from   client clt
  4  ,      action acn
  5  ,      jobs   jos
  6  where  jos.client_id = clt.client_id
  7  and    acn.action_id = jos.action_id
  8  group  by clt.address;

ADDRESS                        MIN(ACN.PRIORITY)
------------------------------ -----------------
7 High St                                      3
88 Pudding Lane                                2
1 Acacia Ave                                   1