Suatu Relationship dikatakan sebagai One To Many yaitu jika tabel yang merujuk di antara dua table, sebagai ilustrasi coba perhatikan gambar berikut:

erd

Jika di perhatikan sama ya seperti One To One?? yapp betul secara assosiasi entity memang sama tapi secara data berbeda. artinya

Di satu row order dalam tabel bisa memiliki banyak order_details dan di satu row pada table order_details hanya ada di satu order

Berikut adalah implementasi menggunakan Oracle Database:

Jadi untuk One To Many Relationship kita membutuhkan setidaknya 2 table. Jika di jalankan maka hasilnya seperti berikut:

sqlplus toko_online/toko_online@xepdb1

SQL*Plus: Release 18.0.0.0.0 - Production on Mon Mar 22 03:03:24 2021
Version 18.4.0.0.0

Copyright (c) 1982, 2018, Oracle.  All rights reserved.

Last Successful login time: Mon Mar 22 2021 02:51:08 +00:00

Connected to:
Oracle Database 18c Express Edition Release 18.0.0.0.0 - Production
Version 18.4.0.0.0

SQL> SET LONG 20000 LONGCHUNKSIZE 20000 PAGESIZE 0 LINESIZE 1000 FEEDBACK OFF VERIFY OFF TRIMSPOOL ON;
SQL> SET PAGESIZE 14 LINESIZE 100 FEEDBACK ON VERIFY ON;

SQL> col trx_id format a2;
SQL> col cust_name format a20;
SQL> col item_name format a20;
SQL> col price_sell format a15;
SQL> col qty format a5;
SQL> col sub_total format a20;

SQL> select o.id                                       as trx_id,
       o.cust_name                                     as cust_name,
       od.item                                         as item_name,
       to_char(od.price, '999G999G999')                as price_sell,
       to_char(od.qty, '999G999')                      as qty,
       to_char((od.price * od.qty), '999G999G999G999') as sub_total
from orders o
         left join order_details od on o.id = od.order_id
order by trx_id;

TR CUST_NAME            ITEM_NAME             PRICE_SELL      QTY   SUB_TOTAL
-- -------------------- --------------------- --------------- ----- --------------------
1  Dimas Maryanto       Macbook Pro 13"        25,000,000      1          25,000,000
1  Dimas Maryanto       iPad Pro 11" (WIFI+C   15,000,000      1          15,000,000
                        elular)                                
1  Dimas Maryanto       Apple Pencil 2nd gen    2,200,000      1           2,200,000
1  Dimas Maryanto       iPhone 7 Plus (32 GB)    2,200,000     1           2,200,000
2  Muhamad Yusuf        Macbook Pro 15"        34,000,000      1          34,000,000
2  Muhamad Yusuf        iPhone 5 (24 GB)       15,000,000      1          15,000,000

6 rows selected.

SQL>