# ISNUMERIC

A numeric function that tests for a valid number.

## Synopsis

```ISNUMERIC(check-expression)
```

### Arguments

Argument Description
check-expression The expression to be evaluated.

ISNUMERIC returns the SMALLINT data type.

## Description

ISNUMERIC evaluates check-expression and returns one of the following values:

• Returns 1 if check-expression is a valid number. A valid number can either be a numeric expression or a string that represents a valid number.

• A numeric expression is first converted to canonical form, resolving multiple leading signs; therefore, a numeric expression such as +-+++34 is a valid number.

• A numeric string is not converted before evaluation. A numeric string must have at most one leading sign to evaluate as a valid number. A numeric string with a trailing decimal point evaluates as a valid number.

• Returns 0 if check-expression is not a valid number. Any string that contains a non-numeric character is not a valid number. A numeric string with more than one leading sign, such as '+-+++34', is not evaluated as a valid number. An InterSystems IRIS encoded list always returns 0, even if its element(s) are valid numbers. An empty string ISNUMERIC('') returns 0.

• Returns NULL if check-expression is NULL. ISNUMERIC(NULL) returns null.

ISNUMERIC generates an SQLCODE -7, exponent out of range error if a scientific notation exponent is greater than 308 (308 – (number of integers - 1)). For example, ISNUMERIC(1E309) and ISNUMERIC(111E307) both generate this error code. If an exponent numeric string less than or equal to '1E145' returns 1; an exponent numeric string greater than '1E145' returns 0.

The ISNUMERIC function is very similar to the ObjectScript \$ISVALIDNUM function. However, these two functions return different values when the input value is NULL.

## Examples

In the following example, all of the ISNUMERIC functions return 1:

```SELECT ISNUMERIC(99) AS MyInt,
ISNUMERIC('-99') AS MyNegInt,
ISNUMERIC('-0.99') AS MyNegFrac,
ISNUMERIC('-0.00') AS MyNegZero,
```SELECT Name,