The SUM function in SQL is an aggregate function used to calculate the total sum of numeric values in a column or expression over a set of rows.

? Syntax

SUM(expression)

• expression: A numeric column or an expression that evaluates to a number.

? What it does

• Adds up all the values in the specified column or expression.

• Ignores NULL values.

• Returns a single numeric result.

? Example Usage

Suppose you have a table Sales with a column Amount:

SELECT SUM(Amount) AS TotalSalesFROM Sales;

This returns the total sum of all sales amounts.

More Examples

1. Sum with WHERE clause:

SELECT SUM(Amount) AS TotalSales2023FROM SalesWHERE YEAR(SaleDate) = 2023;

2. Sum grouped by category:

SELECT Category, SUM(Amount) AS TotalCategorySalesFROM SalesGROUP BY Category;

Notes

• SUM works only with numeric data types.

• Can be combined with GROUP BY to get sums per group.

• Returns NULL if there are no rows (no matching data).

If you'd like, I can show you how to use SUM in more complex queries or with specific SQL dialects!