There is one more function that has to be implemented - function for summing values. For example, we may want to calculate the total revenue for a certain item.

To sum values in column use `SUM` function followed by column which values you want to sum. For our abstract example,

SELECT SUM(revenue)
FROM sells
WHERE item = 'Sofa'

> Please note, that `SUM` function works only with numeric columns.

SQL is a domain-specific programming language widely used by data scientists, analysts, etc for manipulating and extracting necessary data. Nowadays, SQL is a must-have point in the CV for every potential analyst, data scientist. In this course, you will be introduced to the very basics of SQL.

In this section, you will be introduced to the very basics of SQL: extracting one or multiple columns from a database.

In this section, you will learn how to filter observations so only necessary rows will be extracted.

In this section, you will learn about the usage of different aggregating functions for your table, such as minimum, maximum, average... 

In this section, you will learn how to sort your table, even having filters and aggregate functions applied to a table.

In this section, you will learn about grouping observations and usage of this principle.

This chapter is designed for users who have completed the previous sections and want to consolidate knowledge.

SUMming values

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