Question

Please help me to write a SQL query to extract unique orders from below tables. To do that I Have prepared a SQL query. It’s working fine but in some place its returning some duplicate rows as some orders have more than one products.

For Example:

Customer can buy “IPAD” in one order. However, if they purchase “Ipad” and “Android” as bundle they will receive 50% discount and they can save money. In this case, we will get two products under 1 order. However, customer will pay as one product(i.e $120). To allocate order properly, we have created an extra row for the extra product(if products two). If bundle contain three products, it will create three rows in “product_orders” table respectively.

Example “product_orders” table for multiple products:

id orders_id product_id qty
 1   3      2         1
 2   2      1         1
 3   3      3         1

Please check above example table, one order_id copied twice for the bundle order.
If we able to extract one order information, we will get the whole bundle information. So, we don’t need the extra row.

The Query I have applied:

Select 
    orders.id, 
    orders.order_price, 
    orders.purchase_date,
    customers.email, 
    product_orders.qty, 
    products.name 
from 
    orders 
    INNER JOIN product_orders on orders.id=product_orders.orders_id 
    INNER JOIN products on product_orders.product_id=products._id 
    INNER JOIN customers on orders.customer_id =customers.id

Result of the above query:**

Id  order_price  purchase_date      email        qty         name 
3  20         12/6/2011     [e-mail]             1   Ipad

3  20         12/6/2011     [e-mail]             1   Android
1  40         10/5/2011     [e-mail]             2  Laser hair remover

Required Result:

remove duplicate order ID

Id  order_price  purchase_date      email        qty         name 
    3  20         12/6/2011     [e-mail]             1   Ipad


    1  40         10/5/2011     [e-mail]             2  Laser hair remover

Table 1: orders

id  customer_id order_price purchase_date
1   1                   0.20    12/6/2011
2   2                   0.20    12/6/2011
3   1                   0.20    12/6/2011
4   1                   0.20    12/6/2011
5   1                   0.20    12/7/2011
6   3                   199.00  12/7/2011
7   4                   199.00  12/7/2011
8   5                   199.00  12/7/2011
9   6                   199.00  12/7/2011
10  7                   199.00  12/7/2011

Table 2 : customers

id  email                   name
1   [e-mail] aa
2   [e-mail] bb
3   [e-mail]          cc
4   [e-mail]    dd
5   [e-mail]  ee
6   [e-mail]  ff
7   [e-mail]         ss

table 3: products

id  name
1   A Home Portable Laser Hair Remover
2   Ipad
3   android
4   Asus
5   s
6   10 inch Android
7   A Fabric Steamer Cleaner
8   A Magnetic Fly Screen Door
9   pillopw
10  LCD

table 4: product_orders

id orders_id product_id qty
    1   1      1         1
    2   3      3         1
    3   3      4         1
    4   4      1         1
    5   4      2         1
    6   6      1         1
    7   7      1         1
    8   4      2         1
    9   4      3         1
    10  10     1         1

Please help me to extract only 1 order from “product_orders” table and the query will omit other extra rows

Answer 1

Add extra subquery which gets only one product per order_id

Select 
    orders.id, 
    orders.order_price, 
    orders.purchase_date,
    customers.email, 
    product_orders.qty, 
    products.name 
from 
    orders 
    INNER JOIN product_orders on orders.id=product_orders.orders_id 
    INNER JOIN
    (
        SELECT orders_id, MIN(Product_ID) prodID
        FROM product_orders
        GROUP BY orders_id
    ) c ON product_orders.orders_ID = c.orders_id AND
            product_orders.Product_ID = c.prodID
    INNER JOIN products on product_orders.product_id=products.id 
    INNER JOIN customers on orders.customer_id =customers.id

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