Redaguoti

Bendrinti naudojant

BINARY_CHECKSUM (Transact-SQL)

  • Straipsnis

Applies to: SQL Server Azure SQL Database Azure SQL Managed Instance Azure Synapse Analytics SQL analytics endpoint in Microsoft Fabric Warehouse in Microsoft Fabric

Returns the binary checksum value computed over a row of a table or over a list of expressions.

Transact-SQL syntax conventions

Syntax

BINARY_CHECKSUM ( * | expression [ ,...n ] )

Note

This syntax is not supported by serverless SQL pool in Azure Synapse Analytics.

Arguments

*
Specifies that the computation covers all the table columns. BINARY_CHECKSUM ignores columns of noncomparable data types in its computation. Noncomparable data types include

  • cursor
  • image
  • ntext
  • text
  • xml

and noncomparable common language runtime (CLR) user-defined types.

expression
An expression of any type. BINARY_CHECKSUM ignores expressions of noncomparable data types in its computation.

Return Types

int

Remarks

BINARY_CHECKSUM(*), computed on any row of a table, returns the same value as long the row isn't modified later. BINARY_CHECKSUM satisfies the properties of a hash function: when applied over any two lists of expressions, returns the same value if the corresponding elements of the two lists have the same type and are equal when compared using the equals (=) operator. For this definition, we say that null values, of a specified type, compare as equal values. If at least one of the values in the expression list changes, the expression checksum can also change. However, this change isn't guaranteed, and so to detect whether values have changed, we recommend use of BINARY_CHECKSUM only if your application can tolerate an occasional missed change. Otherwise, consider using HASHBYTES instead. With a specified MD5 hash algorithm, the probability that HASHBYTES will return the same result, for two different inputs, is much lower than BINARY_CHECKSUM.

BINARY_CHECKSUM can operate over a list of expressions, and it returns the same value for a specified list. BINARY_CHECKSUM applied over any two lists of expressions returns the same value if the corresponding elements of the two lists have the same type and byte representation. For this definition, null values of a specified type are considered to have the same byte representation.

BINARY_CHECKSUM and CHECKSUM are similar functions. They can be used to compute a checksum value on a list of expressions, and the order of expressions affects the resultant value. The order of columns used for BINARY_CHECKSUM(*) is the order of columns specified in the table or view definition. This ordering includes computed columns.

BINARY_CHECKSUM and CHECKSUM return different values for the string data types, where locale can cause strings with different representation to compare as equal. The string data types are

  • char
  • nchar
  • nvarchar
  • varchar

or

  • sql_variant (if the base type of sql_variant is a string data type).

For example, the strings "McCavity" and "Mccavity" have different BINARY_CHECKSUM values. In contrast, for a case-insensitive server, CHECKSUM returns the same checksum values for those strings. You should avoid comparison of CHECKSUM values with BINARY_CHECKSUM values.

BINARY_CHECKSUM supports any length of type varbinary(max) and up to 255 characters of type nvarchar(max).

Examples

This example uses BINARY_CHECKSUM to detect changes in a table row.

USE AdventureWorks2022;  
GO  
CREATE TABLE myTable (column1 INT, column2 VARCHAR(256));  
GO  
INSERT INTO myTable VALUES (1, 'test');  
GO  
SELECT BINARY_CHECKSUM(*) from myTable;  
GO  
UPDATE myTable set column2 = 'TEST';  
GO  
SELECT BINARY_CHECKSUM(*) from myTable;  
GO

See also

Aggregate Functions (Transact-SQL)
CHECKSUM_AGG (Transact-SQL)
CHECKSUM (Transact-SQL)
HASHBYTES (Transact-SQL)