Sum In SQL

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

The SUM function in SQL is used to calculate the total of numeric values in a column. It's a crucial aggregate function for summarizing data and performing calculations on sets of rows.

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Description

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The SUM function in SQL is a powerful tool for calculating the total of numeric values within a specific column of a table. It's an aggregate function, meaning it operates on a set of rows and returns a single result. This is essential for tasks like calculating total sales, total inventory, or any other sum of numerical data. It's a fundamental part of data analysis and reporting in SQL databases. To use SUM, you specify the column you want to sum and optionally a WHERE clause to filter the rows considered in the calculation. For example, you might want to find the total sales for a particular product category or the total amount spent by a specific customer. The SUM function is incredibly versatile and can be combined with other SQL functions and clauses to create complex queries for more sophisticated analyses. It's important to note that SUM will return NULL if all the values in the specified column are NULL. Also, if you try to sum non-numeric data, you'll get an error.

Why Sum In SQL is important

The SUM function is crucial for summarizing data and performing calculations on sets of rows. It's essential for reporting, analysis, and decision-making in various business applications.

Sum In SQL Example Usage


-- Sample table: Sales
CREATE TABLE Sales (
    OrderID INT PRIMARY KEY,
    ProductID INT,
    Quantity INT,
    Price DECIMAL(10, 2)
);

-- Insert some sample data
INSERT INTO Sales (OrderID, ProductID, Quantity, Price)
VALUES
(1, 101, 2, 10.99),
(2, 102, 5, 25.50),
(3, 101, 3, 10.99),
(4, 103, 1, 50.00);

-- Calculate the total revenue
SELECT SUM(Price * Quantity) AS TotalRevenue
FROM Sales;

Sum In SQL Syntax

Common Mistakes

Forgetting to use the aggregate function (SUM) in the SELECT statement.
Trying to use SUM on a column containing non-numeric data.
Not specifying a column to sum.
Using SUM without a GROUP BY clause when dealing with multiple categories or groups of data.

Frequently Asked Questions (FAQs)

Why does SQL SUM return NULL when all values are NULL?

The SUM function aggregates over the set of rows you specify. If every value in the target column is NULL, there are no numeric values for the engine to add, so the result is NULL instead of 0. To avoid unexpected NULLs, wrap the column in COALESCE (e.g., SUM(COALESCE(amount,0))) or ensure the query filters out entirely NULL rows.

How do I calculate a conditional total with SUM?

Add a WHERE clause to restrict the rows fed into the aggregate. For example, SELECT SUM(sales) FROM orders WHERE category = 'Electronics'; totals only the sales that belong to the Electronics category. You can combine multiple conditions, subqueries, or JOINs to create highly specific roll-ups.

Can Galaxy help me write and optimize SUM queries?

Yes. Galaxy’s context-aware AI copilot autocompletes syntax, suggests COALESCE patterns to guard against NULL totals, and flags non-numeric columns before you run the query. You can also save and endorse your SUM queries in a Collection so teammates reuse the exact logic without pasting SQL in Slack or Notion.