SUM() - This function returns the sum of the values in a specific column. Let's take a look at the following example. 

SELECT SUM(population) 
FROM country 
WHERE continent='Asia';


**Explanation:** The SUM() function returns the sum of the population of all countries in Asia from the `country` table.

In this section, we will learn how to use the SQL SELECT statement to get a single table column, multiple table columns, and all table columns. We will also find out how to return unique values.

In this section, we will learn how to sort retrieved data using the ORDER BY clause. This clause, which must be the last in the SELECT statement, can be used to sort data on one or more columns as needed.\n

In this section, we will learn how to filter returned data using the SELECT statement’s WHERE clause. We will learn how to test for equality, inequality, more and less significant than value ranges, and NULL values.

In this section, we will learn how to combine WHERE clauses with the AND and OR operators. We will also find out how the NOT operator works.\n\n\n

In this section, we will learn what the SQL aggregate functions are and how to use them to summarize table data.