What if you want to know the exact number of observations in your database? Counting manually sounds like a very very bad idea.

Fortunately, SQL has the built-in functionality of counting rows. To count the number of rows in the whole dataset use `COUNT *`. For example, we can count the total number of our website being visited by using the following query:

> Please note, that for counting the total number of rows you must place `*` within parenthesis, like `COUNT(*)`.

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.

How many?

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