The rule for assigning NULL values to variables or table columns is simple: Use keyword "NULL" directly as normal values. Specifically,

* "NULL" can be used in SET statements to assign NULL values to variables.

* "NULL" can be used in SET clauses in UPDATE statements.

* "NULL" can be used in value lists in INSERT statements.

* "NULL" can be used in parameter lists when calling stored procedures or functions.

The tutorial script below gives you some good examples:

USE GlobalGuideLineDatabase;

GO

-- assign NULL values to variables

DECLARE @birth_date DATETIME;

SET @birth_date = NULL;

SELECT @birth_date;

GO

-----------------------

NULL

-- assign NULL values to columns

UPDATE ggl_links SET notes = NULL;

GO

(8 row(s) affected)

-- assign NULL values to parameters

EXEC sp_help NULL;

GO

Name

----------------

ggl_links_dump

ggl_links_top

ggl_links_view

...