Alias scope in SQL query

Why is it that once an alias is declared for the table that the fully qualified name can no longer be used? I find this curious and am just interested if anyone has any insight into why this is or if this is just T-SQL.

Seems like a scope issue, that once an alias is declared below for the tables (i and p) that the fully qualified names are no longer valid.

Thanks.

USE AdventureWorks2012;
GO
SELECT i.SalesOrderDetailID
FROM SalesLT.SalesOrderDetail AS i
INNER JOIN SalesLT.SalesOrderHeader AS p
ON SalesLT.SalesOrderDetail.SalesOrderID = SalesLT.SalesOrderDetail.SalesOrderID

results in an error

but
USE AdventureWorks2012;
GO
SELECT SalesOrderDetailID
FROM SalesLT.SalesOrderDetail
INNER JOIN SalesLT.SalesOrderHeader
ON SalesLT.SalesOrderDetail.SalesOrderID = SalesLT.SalesOrderDetail.SalesOrderID

is fine
and this is also fine

USE AdventureWorks2012;
GO
SELECT i.SalesOrderDetailID
FROM SalesLT.SalesOrderDetail AS i
INNER JOIN SalesLT.SalesOrderHeader AS p
ON i.SalesOrderID = p.SalesOrderID
alexmac05Asked:
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QlemoConnect With a Mentor Batchelor, Developer and EE Topic AdvisorCommented:
This is a general "feature" of all SQL dialects I know of, and not restricted to T-SQL. Once you introduce an alias, you can't use the real name. That is because you rename the internal object name. It isn't just an alias, it is the name.
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awking00Commented:
One of the primary reasons for using an alias is so you don't have to use the fully qualified name and why would you create an alias if you're not going to use it?
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alexmac05Author Commented:
Thank you to both of you for answering.
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