DECLARE @Foo TABLE (Col VARCHAR(10))
INSERT @Foo
VALUES
('ccode'),
('1000'),
('1000f'),
('1002'),
('1004f'),
('12321412g'),
('21334123h'),
('1234512f')

-- NO values with a-z
SELECT *
FROM @Foo
WHERE Col NOT LIKE '%[a-z]%'

--OR, olny values that are 0-9
SELECT *
FROM @Foo
WHERE Col NOT LIKE '%[^0-9]%'