checksum

Returns the checksum value computed over a row of a table, or over a list of expressions. CHECKSUM is intended for use in building hash indexes.

CHECKSUM returns an error if any column is of noncomparable data type. Noncomparable data types are text, ntext, image, XML, and cursor, and also sql_variant with any one of the preceding types as its base type.

The following example uses CHECKSUM_AGG to detect changes in the Quantity column of the ProductInventory table in the AdventureWorks2008R2 database.

--Get the checksum value before the column value is changed.
USE AdventureWorks2008R2;
GO
SELECT CHECKSUM_AGG(CAST(Quantity AS int))
FROM Production.ProductInventory;
GO
Here is the result set.

------------------------
262
UPDATE Production.ProductInventory
SET Quantity=125
WHERE Quantity=100;
GO
--Get the checksum of the modified column.
SELECT CHECKSUM_AGG(CAST(Quantity AS int))
FROM Production.ProductInventory;
Here is the result set.
-----------------------
287