What is NULL in SQL? How to use Nulls in Query? Example Tutorial

Hello guys, NULL is a very important concept in SQL as it indicate absence of values. A column can be Nullable or not Nullable, which means it can either contains null values or not. For a column which contains optional values like Car in Person table, you can use Null to indicate a person doesn't have car. 

While this part is easy, the real trouble comes when you need to query and deal with values which may have nulls. For an SQL developer it's important to find all rows where a certain column is Null, now how to compare Null as simply checking with = or != is not enough. 

This article will describe the complications that might arise when working with SQL NULL values, as well as some tips for resolving them.