What is ISNUMERIC in SQL Server 2008R2?

Definition:-

ISNUMERIC () is a function to determines where an expression is valid numeric type or not.

ISNUMERIC return 1 when input expression is valid numeric data type, otherwise it return 0.

Syntax:-

ISNUMERIC (expression)

ReturnType:-

Int

Note:-

ISNUMERIC returns 1 for some characters that are not numbers, such as plus (+), minus (-), and valid currency symbols such as the dollar sign ($).

Example:-

Select ISNUMERIC('123')

Select ISNUMERIC(123)

Output:

1

References taken from MSDN.