Problem with SQL query

Hi,

My SQL query that i have used for a long time now, seems to be timing out when i open it.

It works fine if i in edit mode, execute query. But as soon as i'm in view mode, it times out.

Can you advise what could be the problem please?

SQL Query below.

Thank you.

SELECT

Customers.ID,

Customers.Name,

Customers.Email,

Customers."Sales Responsible US",

Customers."Sales Responsible",

Customers."website_id",

ISNULL(Orders_New.row_invoiced, '-1'),

Orders_New.status,

Customers."Group",

Orders_New.coupon_code,

Orders_New.created_at

FROM "Customers" LEFT JOIN Orders_New ON Customers.ID = Orders_New.customer_id