(Databases-MySQL) NULL Value

< Null Value in MySQL >

What is a NULL Value? 

:  NULL value is a filed with no value. NULL is not value, it's just a place holder 

** Therefore, we can't compare between NULL values! 

Null is unknown, so they can't be same !   null != null 

 

Can we test for NULL?

: Yes, it's possible to test for using IS NULL & IS NOT NULL 

 

 

NULL Value with Groung and Aggregating 

: Nulls are counted when grouping, but ignored when aggregating! 

 

 

 

 

 

 

Reference : 

 

https://www.tutorialspoint.com/sql/sql-null-values.html

SQL - NULL Values

https://www.w3schools.com/SQl/sql_null_values.asp

SQL NULL Values - IS NULL and IS NOT NULL