SQL Correlated Subqueries

Demonstrates SQL correlated subqueries.

[User]

Loving these videos, your explanations are excellent!

[xrwflmf]

why c.customerid and not o.customerid? are they both interchangeable?

[jayjayf]

Can't you just use group by in the subquery?

[marcinx]

Would below be the same?

SELECT c.ContactName, c.OrderDate,
(select Max(OrderDate) from orders o
where o.CustomerID = c.CustomerID) sq
from Customers c

[cellobix]

Is there a reason not to do

select ContactName, max(OrderDate)
from customers c join orders o
on c.CustomerID = o.CustomerID
group by c.CustomerID

?