Query to achieve exclusively one-to-one relation data

Question

Hi,
I am looking for a query to find rows with one-to-one relation ship.
To make it simple here is the sample code.
CREATE TABLE my_storegroup_gbcust
  store_grp_id        NUMBER(6)                 NOT NULL,
  group_buy_cust_num  NUMBER(5)                 NOT NULL
INSERT INTO my_storegroup_gbcust (store_grp_id, group_buy_cust_num ) VALUES (1002, 70001);
INSERT INTO my_storegroup_gbcust (store_grp_id, group_buy_cust_num ) VALUES (1003, 70001);
INSERT INTO my_storegroup_gbcust (store_grp_id, group_buy_cust_num ) VALUES (1004, 70001);
INSERT INTO my_storegroup_gbcust (store_grp_id, group_buy_cust_num ) VALUES (1005, 70001);
INSERT INTO my_storegroup_gbcust (store_grp_id, group_buy_cust_num ) VALUES (1006, 70001);
INSERT INTO my_storegroup_gbcust (store_grp_id, group_buy_cust_num ) VALUES (2001, 65000);
INSERT INTO my_storegroup_gbcust (store_grp_id, group_buy_cust_num ) VALUES (28001, 21800);
INSERT INTO my_storegroup_gbcust (store_grp_id, group_buy_cust_num ) VALUES (35001, 27010);
INSERT INTO my_storegroup_gbcust (store_grp_id, group_buy_cust_num ) VALUES (35001, 37927);
select * from MY_STOREGROUP_GBCUST
STORE_GRP_ID     GROUP_BUY_CUST_NUM
1002               70001
1003               70001
1004               70001
1005               70001
1006               70001
2001               65000
28001               21800
35001               27010
35001               37927The data in the table describes 3 types of relations.
Many-to-One => Many store groups to one group buy => Example : 1002,1003,1004,1005,1006 mapped to 7001
One-to-One => One store group to one group buy only => Example : 2001 mapped to 65000 ; 28001 mapped to 21800
One-to-Many => One store group to many group buy => Example: 35001 mapped to 27010,37927
Now I am able to achieve through query One-to-Many and Many-to-One by as below :
select group_buy_cust_num,count(*) from MY_STOREGROUP_GBCUST group by group_buy_cust_num having count(*) > 1
select store_grp_id,count(*) from MY_STOREGROUP_GBCUST group by store_grp_id having count(*) > 1    But how do I get One-to-One exclusively.
Thanks,
Raj.

Answer 1

This is what I get by changing > to = sign.
select group_buy_cust_num,count(*) from MY_STOREGROUP_GBCUST group by group_buy_cust_num having count(*) = 1
GROUP_BUY_CUST_NUM     COUNT(*)
21800               1
27010               1
65000               1
37927               1
select store_grp_id,count(*) from MY_STOREGROUP_GBCUST group by store_grp_id having count(*) = 1
STORE_GRP_ID     COUNT(*)
28001               1
1005               1
2001               1
1003               1
1002               1
1004               1
1006               1But I need just this
STORE_GRP_ID     COUNT(*)
2001               1
28001               1