The ISNUMERIC () detects whether a digital

ISNUMERIC (expression The)
when the input expression is a valid thanks to a number of integer, floating point, money, or decimal type, then ISNUMERIC returns 1; 0 otherwise. 1 to ensure that the return value can be converted into a expression of the digital type.
Note that the determination is 0 and 1 return
the same usage it is ISDATE (expression)
, such as: case when ISNUMERIC (field) = 1 then 'digital' else 'character' end