SQL Sum Function

How do you calculate the sum of values in a SQL table?

The SQL SUM function is used to calculate the total sum of values in a specific column of a table. It's a crucial aggregate function for summarizing data.

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Description

Example H2

Example H3

The SUM function in SQL is a powerful tool for quickly calculating the total of numerical values within a column of a table. It's a core part of aggregate functions, which are used to perform calculations on groups of rows. Imagine you have a sales database; using SUM, you can easily find the total revenue generated in a specific month or by a particular salesperson. This function is essential for tasks like financial reporting, inventory management, and data analysis. It's particularly useful when you need to get a concise summary of a large dataset. The SUM function works by adding up all the values in the specified column, ignoring any NULL values. This is a critical point to remember, as NULLs won't contribute to the sum.

Why SQL Sum Function is important

The SUM function is crucial for summarizing data and generating reports. It allows for quick calculation of totals, which is essential for business decisions and data analysis. It's a fundamental building block for more complex queries and reports.

SQL Sum Function Example Usage


-- Using SUBSTRING and CHARINDEX (for a fixed delimiter)
DECLARE @inputString VARCHAR(100) = 'apple,banana,orange';
DECLARE @delimiter CHAR(1) = ',';
DECLARE @startIndex INT = 1;
DECLARE @endIndex INT;

WHILE @startIndex <= LEN(@inputString)
BEGIN
    SELECT @endIndex = CHARINDEX(@delimiter, @inputString, @startIndex);
    IF @endIndex = 0
        SET @endIndex = LEN(@inputString) + 1;
    SELECT SUBSTRING(@inputString, @startIndex, @endIndex - @startIndex);
    SET @startIndex = @endIndex + 1;
END;

-- Using a User-Defined Function (for more complex scenarios)
CREATE FUNCTION dbo.SplitString (@inputString VARCHAR(MAX), @delimiter CHAR(1))
RETURNS @output TABLE (value VARCHAR(MAX))
AS
BEGIN
    DECLARE @startIndex INT = 1;
    DECLARE @endIndex INT;

    WHILE @startIndex <= LEN(@inputString)
    BEGIN
        SELECT @endIndex = CHARINDEX(@delimiter, @inputString, @startIndex);
        IF @endIndex = 0
            SET @endIndex = LEN(@inputString) + 1;
        INSERT INTO @output (value) VALUES (SUBSTRING(@inputString, @startIndex, @endIndex - @startIndex));
        SET @startIndex = @endIndex + 1;
    END;
    RETURN;
END;

-- Example usage of the UDF
SELECT value FROM dbo.SplitString('apple,banana,orange', ',');
DROP FUNCTION dbo.SplitString; -- Important: Clean up after use

SQL Sum Function Syntax

Common Mistakes

Forgetting to specify the column to sum. Incorrect syntax can lead to errors.
Misunderstanding how NULL values are handled. NULLs are excluded from the calculation.
Not using aggregate functions with GROUP BY when needing to calculate sums for different groups.

Frequently Asked Questions (FAQs)

Why does SQL SUM ignore NULL values, and how can I include them if needed?

By design, the SUM aggregate skips NULLs so that unknown or missing values don’t distort the total. If you want to treat NULLs as zeros, wrap the target column with COALESCE(column_name, 0) or a similar function before summing. Example: SELECT SUM(COALESCE(revenue,0)) FROM sales;

What real-world business tasks rely on the SUM function?

SUM powers everyday analytics such as calculating monthly revenue, tracking total units sold, aggregating inventory counts, or generating financial reports for stakeholders. Any scenario that needs a quick numeric roll-up across many rows—especially in sales, finance, or supply-chain data—benefits from SUM.

How does Galaxy make writing SUM queries faster and safer?

Galaxy’s context-aware AI copilot autocompletes column names, suggests GROUP BY clauses, and flags potential NULL pitfalls while you type. You can share and “Endorse” vetted SUM queries inside Galaxy Collections, eliminating copy-and-paste errors in Slack or Notion and ensuring the whole team trusts the same revenue or inventory totals.