WHERE
клаузата се изпълнява първа. Опитайте:
DECLARE @table table (loc varchar(10))
INSERT INTO @table VALUES
('134a'), ('123'), ('abc'), ('124')
SELECT *
FROM (
SELECT * FROM @table
) as a
WHERE ISNUMERIC(loc) = 1 and CAST(loc as INT) BETWEEN 100 AND 200