Chế độ xem SQL:Nối các bảng mà không làm cho dữ liệu trùng lặp trên mọi hàng?

Bạn cần sử dụng UNION (thực ra là UNION ALL) trong trường hợp này.

select a.name as account_Name, 
       p.description as property_DESCRIPTION, 
       p.address as property_ADDRESS, 
       null as vehicles_DESCRIPTION,
       null as vehicles_MAKE, 
       null as vehicles_MODEL
    from Accounts a
        inner join Properties p
            on a.accountid = p.accountid
UNION ALL   
select a.name as account_Name, 
       null as property_DESCRIPTION, 
       null as property_ADDRESS, 
       v.description as vehicles_DESCRIPTION,
       v.make as vehicles_MAKE, 
       v.model as vehicles_MODEL
    from Accounts a
        inner join vehicles v
            on a.accountid = v.accountid