SQL Isnumeric

How do you check if a value is a valid numeric type in SQL?

The ISNUMERIC function in SQL Server checks if an expression evaluates to a valid numeric data type. It's crucial for data validation, ensuring that columns contain expected numeric values.

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Description

Example H2

Example H3

The ISNUMERIC function in SQL Server is a built-in function used to determine whether an expression can be evaluated as a numeric value. It's particularly useful in data validation, ensuring that data entered into a database column conforms to the expected numeric format. This function is essential for preventing errors and maintaining data integrity. For example, if you're expecting a price column to only contain numbers, you can use ISNUMERIC to check if the input is a valid number before storing it. It's important to note that ISNUMERIC considers various numeric formats, including integers, decimals, and scientific notation. However, it also considers strings that can be converted to numbers, which might not be ideal in all cases. For instance, it will return TRUE for strings like '+123' or '12.34'. Therefore, it's often combined with other checks or validation rules to ensure the data meets specific requirements. A more robust approach might involve using TRY_CONVERT to attempt conversion to a numeric type and checking for errors.

Why SQL Isnumeric is important

ISNUMERIC is vital for data validation, preventing invalid data from entering the database. It helps maintain data integrity and ensures that queries operate on expected numeric values, reducing the risk of unexpected errors.

SQL Isnumeric Example Usage


-- Example using IIF to assign a status based on order amount
CREATE TABLE Orders (
    OrderID INT PRIMARY KEY,
    OrderAmount DECIMAL(10, 2),
    OrderDate DATE
);

INSERT INTO Orders (OrderID, OrderAmount, OrderDate) VALUES
(1, 100.00, '2023-10-26'),
(2, 50.00, '2023-10-27'),
(3, 200.00, '2023-10-28');

SELECT
    OrderID,
    OrderAmount,
    IIF(OrderAmount > 100, 'High Value', 'Low Value') AS OrderStatus
FROM
    Orders;

SQL Isnumeric Syntax

Common Mistakes

Assuming ISNUMERIC is sufficient for all numeric validation needs.
Not combining ISNUMERIC with other validation checks (e.g., checking for a specific range of values).
Forgetting that ISNUMERIC returns TRUE for strings that can be converted to numbers, even if they aren't strictly numeric.

Frequently Asked Questions (FAQs)

Why does ISNUMERIC sometimes return TRUE for non-standard numeric strings?

ISNUMERIC checks whether a value can be converted to any SQL Server numeric type, including money and scientific-notation variants. Because of this broad scope, strings like "+123", "12.34", or "1e5" evaluate to 1 (TRUE) even if they are not the exact format you want to store. To enforce stricter rules, pair ISNUMERIC with TRY_CONVERT or TRY_CAST to your target type and reject inputs that return NULL.

What numeric formats does ISNUMERIC recognize during validation?

ISNUMERIC returns TRUE for integers (e.g., 42), decimal numbers (e.g., 3.1415), and scientific notation (e.g., 6.02e23). It also accepts currency symbols and signs where conversion is possible. This wide acceptance is useful for general validation but may require additional checks for business-specific formatting rules.

How can Galaxy help me validate numeric columns more reliably than using ISNUMERIC alone?

In Galaxy’s modern SQL editor, the context-aware AI copilot can auto-suggest TRY_CONVERT or TRY_CAST patterns, highlight risky ISNUMERIC usage, and even generate test queries to surface rows that would fail strict conversions. This speeds up writing safer validation code and keeps your team aligned by letting you endorse the finalized query within a shared Galaxy Collection.