Question About NOT EXISTS and IS NULL (or IS NOT NULL)

Hi.
I need some advices about the clauses NOT EXISTS and IS NULL or NOT NULL.
If I have a statement with in the clause WHERE have a field (or a lot of fields) with IS NULL or IS NOT NULL, exist another way to eliminate this or replace with another statement more performance. For example:
SELECT Name, LastName, DateofBirth
FROM Customer
WHERE Name IS NOT NULL
AND LastName IS NOT NULL
AND DateOfBirth I NOT NULL
And the last question is that exist some statement more performance to replace the clauses NOT EXISTS. For example.
SELECT Name, LastName, DateofBirth
FROM Customer
WHERE Name IS NOT NULL
AND LastName IS NOT NULL
AND DateOfBirth I NOT NULL
AND NOT EXISTS ( SELECT Name FROM XXX WHERE XXX.Name = Customer.Name)
Thank.

Check the following article by Brad...
http://www.sql-server-performance.com/tips/t_sql_where_p2.aspx

MohammedU,
I read the article you pointed. It is very helpful. Thanks!
But I still don't know how to re-write the following Where clause. Any suggestions? Thanks! Sheenawhere status not in ('1', '9', '5','6')
and
hpcode not in ('CALO', 'COHF', 'HEPO')and
proccode not like '7%'and
proccode not like '8%'and
proccode not like 'J%'and
proccode not like 'L%'and
proccode not like 'A%'and
proccode not like 'Q%'

For: [quote user="sbright"]where status not in ('1', '9', '5','6') and
hpcode not in ('CALO', 'COHF', 'HEPO')
[/quote]
Ans: You may not change your query because "IN" Keywords applied to 2 different columns.
But For: [quote user="sbright"] and
proccode not like '7%'and
proccode not like '8%'and
proccode not like 'J%'and
proccode not like 'L%'and
proccode not like 'A%'and
proccode not like 'Q%'
[/quote]
Sheena, you can change this by using full text search command like below:WHERE
NOT CONTAINS(proccode , ' "7*" and "8*" and "J*" and "L*" and "A*" and "U*" ')
NOTE: Before running the query you need to create full text index on the procode column.
Thanks,
Sandy.

These two syntactical elements have very different applications:
You can use IS NOT NULL to evaluate the value of a field (or of an expression) within a row of a resultset.
You can use NOT EXISTS to verify that the subquery after it does not return any rows.
To "find unmatched rows", you can use NOT EXISTS or an outer join:

SELECT t1.*
FROM maintable t1
WHERE NOT EXISTS (SELECT t2.* FROM checktable t2 WHERE t2.checkcolumn = t1.checkcolumn)
SELECT t1.*
FROM maintable t1
LEFT JOIN checktable t2 ON t1.checkcolumn = t2.checkcolumn
WHERE t2.checkcolumn IS NULL
Performance should be comparable, so use the syntax you're most comfortable with.