What is JOIN in SQL?

You can use the SQL JOIN command to gather data from two different tables into a single, merged display table that includes these tables’ included columns. You should generally JOIN tables using one or more factors or values to identify them and try again.

You can join two different tables together. The condition in the first table is evaluated for each row in the second table and, if it matches the condition, the row

Let’s say that you have a database of customer information in a table called Customer_Info.

Every time you sell a product to a customer, you record the Customer Number, Product ID, Price, and Amount Paid for that customer.

The details of orders that are placed on the gateway by the customer are stored in another table called the orders table, which contains the Order Number, Order Date, Expected Shipping Date, and Customer Number.

Imagine that a customer places an order and the following thing that you need to find out is its delivery address.

Although the table only displays customer number data, you can use other column names such as “Customer_Number” and “Product_ID” to order

Join the tables Customers and Order_Number products based on the customer’s number information is necessary. To retrieve the customer’s address, you must use the JOIN

In this specific case, the Customer_Number column is used to compare values.

Order_Number	Order_Date	Expected_Shipping_Date	Customer_Number
10345	31-01-2022	10-02-2022	103
10346	30-01-2022	15-02-2022	112
10120	05-02-2022	16-02-2022	114
10325	06-02-2022	10-02-2022	121
11211	08-02-2022	21-02-2022	4110

Use the query shown here to connect all of the order numbers to customer names and addresses:

SELECT
  a.Order_Number,
  b.Customer_Name,
  b.Postal_Code,
  b.Address
FROM orders a
JOIN customers b 
ON a.Customer_Number = b.Customer_Number;

Result:

Order_Number	Customer_Name	Postal_Code	Address
10345	Atelier	44000	54, RueRoyal
10346	Signal	83030	8489 Strong
10120	Collectors	3004	636 Kilda
10325	Baane Mini	4110	Ering Shakkes

Here’s how you would use JOIN to combine multiple tables into one. In this query, SQL uses Customer_Number as the JOIN condition. For each order, the matching customer number from orders is compared to the customer number in the customers table. The customer name, postal code, and address are retrieved from that order.