In SQL, when we want to obtain the sum of a series of numbers or numerical values, we use the SUM function. This function is one of the Aggregation functions in the database that helps in analyzing and categorizing data. For example, suppose we have a table containing sales information for products, and we want to know the total sales amount; this function is precisely suitable for such scenarios.
The SUM function serves as a powerful tool to easily sum a large number of values. In today's world, where data analysis is very important, familiarity with this function is particularly significant, as it can analyze and interpret business information efficiently.
Additionally, the SUM function can work in conjunction with other functions like GROUP BY for better performance. For example, imagine we want to know how much each category of products has sold. The combination of this function with other commands can produce excellent results.
Sometimes, due to the complexity of data, we may need to use several functions in combination. While the primary use of SUM seems simple, in more advanced contexts, it can present challenges that require previous training and experience to resolve successfully.
Below is an example of how to use SUM in a SQL query:
SELECT department, SUM(salary) AS total_salary
FROM employees
GROUP BY department;
SELECT department, SUM(salary) AS total_salary - In this line, the columns department and the sum of salary, which is named total_salary, are selected.
FROM employees - Selects the data from the employees table.
GROUP BY department - The result must be grouped by department so that the sum of each group is calculated.