Question

I have 2 tables

table Customer

• cus_id
• cus_name

table Buying

• buy_id,
• cus_id(FK to Customer),
• price

The result that I want

cus_id, cus_name, buy_id, price

but in case some customers don’t have buy_id. How can I query like this.

cus_id, cus_name, null, null

Answer 1

use LEFT JOIN if you want to display all customer even if he hasn’t buy anything yet.

SELECT  a.*, b.buy_id, b.price
FROM    customer a
        LEFT JOIN buying b
            ON a.cus_id = b.cus_id

To fully gain knowledge about joins, kindly visit the link below:

• Visual Representation of SQL Joins