Possible misunderstanding of purpose of ISNUMERIC()

[brianary]

The purpose of ISNUMERIC() is to determine whether a character field/column will throw errors when cast to a numeric type, not whether a field/column is a valid SSN or CC#, e.g. It doesn't indiscriminately accept - or + or even E, but it does accept -2.1E-3 because cast('-2.1E-3' as float) works and +$.99 because cast('+$.99' as money) works.

This is particularly helpful for migration scripts when changing the datatype of a column from character to numeric, and couldn't be easily accomplished to accept a wide range of legal numeric literals without

numcolumn = case ISNUMERIC(charcolumn) when 1 then cast(charcolumn as float) end

Filtering non-digit chars is the job of not like '[^0-9]'.