How to exclude characters

Question

Within my query, I have a WHERE statement:
WHERE Left(t_item,2) NOT LIKE '%-'
AND Left(t_item,2) NOT LIKE '_%'
This was to exclude the underscore character. I was told this
was the only non number or letter used. Of course now I am finding
out that this is not true and many other characters are used. Is
there a way for me to alter this to say that the left 2 character
MUST be either a letter or a number.

Answer 1

Doesn't look like you can't refer to your column alias in
your WHERE clause.
SELECT DISTINCT Left(t_item,2) AS series
FROM dbo.ttiitm001#companyNumber#
WHERE Left(t_item,1) IN
('0','1','2',...'O','P','Q','R','S','T','U','V','W','X','Y','Z')
AND Right(Left(t_item,2),1) IN
('0','1','2',...'O','P','Q','R','S','T','U','V','W','X','Y','Z')
ORDER BY 1
--or perhaps--
SELECT DISTINCT Left(t_item,2) AS series
FROM dbo.ttiitm001#companyNumber#
WHERE Left(t_item,1) IN
('0','1','2',...'O','P','Q','R','S','T','U','V','W','X','Y','Z')
AND Substring(t_item,2,1) IN
('0','1','2',...'O','P','Q','R','S','T','U','V','W','X','Y','Z')
ORDER BY 1
--or--
SELECT DISTINCT Left(t_item,2) AS series
FROM dbo.ttiitm001#companyNumber#
WHERE Left(t_item,1) IN
('0','1','2',...'O','P','Q','R','S','T','U','V','W','X','Y','Z')
AND Mid(t_item,2,1) IN
('0','1','2',...'O','P','Q','R','S','T','U','V','W','X','Y','Z')
ORDER BY 1
Phil