How can I count in Joins?

Question

Hello,
I have the following table definitions:
--- Tables
CREATE TABLE group_test
(ID number NOT NULL,
group_name varchar2(20));
ALTER TABLE group_test ADD (CONSTRAINT group_test_p primary key (ID));
CREATE TABLE member_of_groups
(group_test_id number not null,
member varchar2(20));
ALTER TABLE member_of_groups ADD (CONSTRAINT gt_id_fk FOREIGN KEY (group_test_id) REFERENCES group_test(ID));
--- Fill in some data
insert into group_test (id,group_name) values(1,'group_1');
insert into group_test (id,group_name) values(2,'group_2');
insert into group_test (id,group_name) values(3,'group_3');
insert into group_test (id,group_name) values(4,'group_4');
insert into group_test (id,group_name) values(5,'group_5');
commit;
insert into member_of_groups (group_test_id,member) values (1,'Miller');
insert into member_of_groups (group_test_id,member) values (1,'Smith');
insert into member_of_groups (group_test_id,member) values (2,'Walker');
insert into member_of_groups (group_test_id,member) values (3,'Almeida');
insert into member_of_groups (group_test_id,member) values (3,'Walton');
insert into member_of_groups (group_test_id,member) values (3,'McScrooge');
insert into member_of_groups (group_test_id,member) values (4,'Hoover');
insert into member_of_groups (group_test_id,member) values (4,'Brando');
insert into member_of_groups (group_test_id,member) values (5,'Walther');
commit;
-------------------- Queries
select all group_test.group_name,member_of_groups.member from group_test, member_of_groups where group_test.id = member_of_groups.group_test_id;
---------- RESULT
GROUP_NAME MEMBER
group_1 Miller
group_1 Smith
group_2 Walker
group_3 Almeida
group_3 Walton
group_3 McScrooge
group_4 Hoover
group_4 Brando
group_5 Walther
select count(1) as counter from group_test, member_of_groups where group_test.id = member_of_groups.group_test_id group by group_test.group_name;
---------- RESULT
COUNTER
2
1
3
2
1
----- PL/SQL-Code
set serveroutput on
DECLARE
     counter number := 0;
     group_store group_test.group_name%TYPE := '';
     mem_store member_of_groups.member%TYPE := '';
BEGIN
     for c_members in (select all group_test.group_name as gn,member_of_groups.member as mem from group_test, member_of_groups where group_test.id = member_of_groups.group_test_id) loop
          IF (group_store = c_members.gn) then
               counter := counter + 1;
          else
               counter := 1;
               group_store := c_members.gn;
               mem_store := c_members.mem;
          end if;
          if (counter > 1) then          -- Output only groups with more than 1 member
               if (counter = 2) then     -- Output of the first row
                    dbms_output.put_line(group_store || '     ' || mem_store || '     1');
               end if;
               dbms_output.put_line(c_members.gn || '     ' || c_members.mem || '     ' || counter);
          end if;
     end loop;
end;
---------- RESULT
group_1 Miller 1
group_1 Smith 2
group_3 Almeida 1
group_3 Walton 2
group_3 McScrooge 3
group_4 Hoover 1
group_4 Brando 2
----------------------------------------- END OF CODE
Now I want to do this with a plain SQL query. Any hints?
Holger
Edited by: user4546673 on 25.11.2009 06:19

Answer 1

user4546673 wrote:
Thank you very much,
Sorry, your solution is not exact the same and this is not working:
select group_test.group_name,member_of_groups.member,
row_number() over(partition by group_test.group_name order by member_of_groups.member) rn
from group_test,member_of_groups where group_test.id = member_of_groups.group_test_id and rn > 1;
ORA-00904: "RN": invalid identifierIt is not what you asked originally. Analytical functions are calculated after rows are fetched, so if you wnat rn > 1, you need to wrap it in in-line view:
SQL> select group_test.group_name,member_of_groups.member,
  2  row_number() over(partition by group_test.group_name order by member_of_groups.member) rn
  3  from group_test,member_of_groups where group_test.id = member_of_groups.group_test_id and rn > 1;
from group_test,member_of_groups where group_test.id = member_of_groups.group_test_id and rn > 1
ERROR at line 3:
ORA-00904: "RN": invalid identifier
select  group_name,
        member
  from  (
         select  group_test.group_name,
                 member_of_groups.member,
                 row_number() over(partition by group_test.group_name order by member_of_groups.member) rn
           from  group_test,
                 member_of_groups
           where group_test.id = member_of_groups.group_test_id
  where rn > 1
  order by group_name,
           rn
GROUP_NAME           MEMBER
group_1              Smith
group_3              McScrooge
group_3              Walton
group_4              Hoover
SQL> SY.