ISNULL (Transact-SQL)

Replaces NULL with the specified replacement value.

Topic link iconTransact-SQL Syntax Conventions

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 be of a type that is implicitly convertible to the type of 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 after it is implicitly converted to the type of check_expression, if the types are different.

Examples

A. Using ISNULL with AVG

The following example finds the average of the weight of all products. It substitutes the value 50 for all NULL entries in the Weight column of the Product table.

USE AdventureWorks;
GO
SELECT AVG(ISNULL(Weight, 50))
FROM Production.Product;
GO

Here is the result set.

-------------------------- 
59.79                      

(1 row(s) affected)

B. Using ISNULL

The following example selects the description, discount percentage, minimum quantity, and maximum quantity for all special offers in AdventureWorks. If the maximum quantity for a particular special offer is NULL, the MaxQty shown in the result set is 0.00.

USE AdventureWorks;
GO
SELECT Description, DiscountPct, MinQty, ISNULL(MaxQty, 0.00) AS 'Max Quantity'
FROM Sales.SpecialOffer;
GO

Here is the result set.

Description       DiscountPct       MinQty      Max Quantity
---------------   -------------     --------    ---------------
No Discount       0.00              0           0
Volume Discount   0.02              11          14
Volume Discount   0.05              15          4
Volume Discount   0.10              25          0
Volume Discount   0.15              41          0
Volume Discount   0.20              61          0
Mountain-100 Cl   0.35              0           0
Sport Helmet Di   0.10              0           0
Road-650 Overst   0.30              0           0
Mountain Tire S   0.50              0           0
Sport Helmet Di   0.15              0           0
LL Road Frame S   0.35              0           0
Touring-3000 Pr   0.15              0           0
Touring-1000 Pr   0.20              0           0
Half-Price Peda   0.50              0           0
Mountain-500 Si   0.40              0           0

(16 row(s) affected)

See Also

Reference

Expressions (Transact-SQL)
IS [NOT] NULL (Transact-SQL)
System Functions (Transact-SQL)
WHERE (Transact-SQL)
COALESCE (Transact-SQL)

Help and Information

Getting SQL Server 2005 Assistance