ISNULL (T-SQL)

Replaces NULL with the specified replacement value.

Syntax

ISNULL(check_expression, replacement_value)

Arguments

check_expression

Is the expression to be checked for NULL. check_expression can be of any type.

replacement_value

Is the expression to be returned if check_expression is NULL. replacement_value must have the same type as check_expresssion.

Return Types

Returns the same type as check_expression.

Remarks

The value of check_expression is returned if it is not NULL; otherwise, replacement_value is returned.

Examples

A. Use ISNULL with AVG

This example finds the average of the prices of all titles, substituting the value $10.00 for all NULL entries in the price column of the titles table.

USE pubs

GO

SELECT AVG(ISNULL(price, $10.00))

FROM titles

GO

Here is the result set:

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

14.24                     

(1 row(s) affected)

B. Use ISNULL

This example selects the title, type, and price for all books in the titles table. If the price for a given title is NULL, the price shown in the result set is 0.00.

USE pubs

GO

SELECT SUBSTRING(title, 1, 15) AS Title, type AS Type,
    ISNULL(price, 0.00) AS Price

FROM titles

GO

Here is the result set:

Title           Type         Price         

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

The Busy Execut business     19.99                     

Cooking with Co business     11.95                     

You Can Combat  business     2.99                      

Straight Talk A business     19.99                     

Silicon Valley  mod_cook     19.99                     

The Gourmet Mic mod_cook     2.99                      

The Psychology  UNDECIDED    0.00                      

But Is It User  popular_comp 22.95                     

Secrets of Sili popular_comp 20.00                     

Net Etiquette   popular_comp 0.00                      

Computer Phobic psychology   21.59                     

Is Anger the En psychology   10.95                     

Life Without Fe psychology   7.00                      

Prolonged Data  psychology   19.99                     

Emotional Secur psychology   7.99                      

Onions, Leeks,  trad_cook    20.95                     

Fifty Years in  trad_cook    11.95                     

Sushi, Anyone?  trad_cook    14.99                     

(18 row(s) affected)

See Also