**NULL** is a special value that matches missed data. It means there is no data inserted into the field.

There are operators to detect whether the value is NULL:
 - `IS NULL`: detects only values that equal to NULL
 - `IS NOT NULL`: detects values that are not NULL.

SELECT title FROM songs
WHERE album IS NOT NULL

>`NULL` does not match 0 or empty line, it only matches data that is missing and does not exist.

> `NULL` values are ignored in the `MIN`, `MAX`, `COUNT`, `AVG`, and `SUM` aggregate functions.

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 Null