**GROUP BY** is an operator that puts rows with the same values of the field in groups. It creates one row for each group, so it makes sense to use some aggregate function in `SELECT`. For example, let's group our songs by singers, and find a number of songs for each `singer`:

SELECT COUNT(Id), singer
FROM songs
GROUP BY singer

This query will return a list of singers, as well as, for each of them, the number of songs. Each singer represents a unit or group, and **COUNT()** aggregate function is applied for records in the group. You can use `GROUP BY` with `ORDER BY`, and also group by multiple columns. Here is a syntax of query:

-- do not run this query
SELECT col1, col2, ...
FROM table
WHERE condition
GROUP BY col1, col2, ...
ORDER BY col1, col2, ...;

This course was created for very beginners in programming, for those who want to start learning such a popular language for work with databases. Nowadays, all the applications and services collect some data and work with it, and basic SQL syntax is a foundation for further work with other Database Management Systems.

Familiarize yourself with database you will work with, and basic syntax to start executing your first queries!

SQL Group By

解答