How to extract the last inserted row in SQL Server?
By definition, a table is an unordered bag of rows (see #3 here). There is no way to ask SQL Server which row was inserted last unless you are doing so in the same batch as the insert. For example, if your table has an IDENTITY column, you can use SCOPE_IDENTITY() (never use @@IDENTITY, since that can be unreliable if you have or will ever add triggers to the source table):

INSERT dbo.table(column) SELECT 1;
SELECT SCOPE_IDENTITY();


More generally, you can use the OUTPUT clause, which doesn't rely on an IDENTITY column (but will still make it difficult to identify which row(s) the clause identifies if there is no PK):

INSERT dbo.table(column) OUTPUT inserted.* SELECT 1;


If you're not talking about the same batch, then the only real way to identify the last row inserted is to use a date/time column where the timestamp of insertion is recorded. Otherwise it is like you emptied a bag of marbles on the floor, then asked someone to enter the room and identify which one hit the floor last. 

You may be tempted or even advised to use the IDENT_CURRENT() function, but I explain here why this is unreliable too.

You could add a column to track this going forward:

ALTER TABLE dbo.table ADD DateInserted DEFAULT CURRENT_TIMESTAMP;


Now you can find the last row(s) inserted by simply:

;WITH x AS (SELECT *, r = RANK() OVER (ORDER BY DateInserted DESC)
   FROM dbo.table)
SELECT * FROM x WHERE r = 1;


(If you don't want ties, you can add a tie-breaking column to the ORDER BY, or you can simply change RANK() to ROW_NUMBER() if you don't care which of the tied rows you get.)

You might make the assumption that the last row inserted is the highest identity value, but this isn't necessarily the case. The identity can be reseeded and it can also be overridden using SET IDENTITY_INSERT ON;.