What Are NULL Values in SQL Server

Q

What Are NULL Values in SQL Server Transact-SQL?

✍: FYIcenter.com

A

A NULL value is a special value that represents an unknown value. SQL Server supports NULL values with the following features:

  • All data types used for table columns support NULL values. In another word, NULL values can be stored in database tables.
  • Individual table columns may be defined to not allow NULL values. In this case, you can not assign NULL values to those columns.
  • "NULL" is a keyword that represent a NULL value in expressions.
  • NULL values can be used directly in SET (assignment) statements.
  • If NULL values are involved in an arithmetic operation, the result will be a numeric NULL.
  • If NULL values are involved in a string operation, the result will be a string NULL.
  • If NULL values are involved in a datetime operation, the result will be a datetime NULL.
  • If NULL values are involved in a bitwise operation, the result will be a binary NULL.
  • If NULL values are involved in a comparison operation, the result will be a Boolean NULL.
  • If NULL values are involved in a Boolean operation, the result could be TRUE, FALSE, or NULL.
  • To test NULL values, you need to use two special operators, IS NULL and IS NOT NULL.
  • Special functions are available to handle NULL values, like ISNULL(), and NULLIF()

 

Working with NULL Values in SQL Server Transact-SQL

⇒⇒SQL Server Transact-SQL Tutorials

2017-02-05, 276👍, 0💬