ISNUMERIC returns 0 for an empty or blank string. Normally that
wouldn't be a cause for concern since an empty string is clearly "not
numeric", but that's not the definition of ISNUMERIC:

SQL Anywhere® Server - SQL Reference
SQL Functions
Alphabetical list of functions
ISNUMERIC function [Miscellaneous]
Tests if a string argument can be converted to a NUMERIC...

...and CAST will happily convert empty and blank strings to zero:
SELECT CAST ( ' ' AS NUMERIC ) displays 0.000000

I suggest editing the Help to describe exactly *what* ISNUMERIC is
doing (I don't think it's "testing" anything, maybe "checking"... :)

Breck The Nit Picker

Breck Carter [Team iAnywhere]
RisingRoad SQL Anywhere and MobiLink Professional Services
The book: