Why should you care?

Orders need customer names — match Orders.CustomerId to Customers.CustomerId without duplicating names into every order row.

See it live — copy this example

Run in SQL Server Management Studio (SSMS) or Azure Data Studio.

USE DataVerse;
IF COL_LENGTH('dbo.Orders', 'CustomerId') IS NULL
    ALTER TABLE dbo.Orders ADD CustomerId INT NULL;
UPDATE dbo.Orders SET CustomerId = 1 WHERE CustomerId IS NULL;
SELECT o.OrderId, c.FullName, o.Amount
FROM dbo.Orders AS o
INNER JOIN dbo.Customers AS c ON c.CustomerId = o.CustomerId;

What happened?

• Only orders with a matching customer appear.
• Alias o/c keeps the query short.
• ON defines the match rule.

Practice next

1. Ensure Customers and Orders share CustomerId values.
2. Run the INNER JOIN.
3. Insert an order with a fake CustomerId and confirm it disappears from INNER JOIN.
4. Filter WHERE o.Amount > 1000 after the join.
5. Join Products to a new OrderItems table when you create it.

Remember

INNER JOIN keeps matches only. Put the relationship in ON. Orphans on either side are excluded.

Order list with customer name

Support screen joins DataVerse Orders to Customers.

Outcome: Agents see who placed each order in one grid.