When working with databases, it is common to perform calculations on the data. One of the most frequently used calculations is the sum operation. In SQL, the SUM function allows you to calculate the sum of values in a column.

To perform the sum operation in a SQL SELECT statement, follow these steps:

1. Start by writing the SELECT statement to retrieve the desired data from the table.
2. Use the SUM function to calculate the sum of values in the specified column.
3. Specify the column name or expression inside the SUM function.
4. Give an alias to the calculated sum using the AS keyword followed by the desired alias name.

Here is an example to illustrate the usage of SUM in a SQL SELECT statement:

SELECT SUM(quantity) AS total_quantity
FROM orders;

In the example above, we are calculating the total quantity of items ordered from the orders table. The quantity column holds the quantity of each item in an order. By using the SUM function and providing the quantity column as the argument, we can retrieve the total sum of all quantities. The calculated sum is given the alias total_quantity using the AS keyword.

By running this SQL query, you will get the total sum of quantities as a result.

Remember to replace quantity and orders with the actual column name and table name in your database.

Using the SUM function in SQL SELECT statements is a powerful way to calculate totals and perform aggregations on your data. It can be used in combination with other functions, such as GROUP BY, to perform more complex calculations and analysis.

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