HASHBYTES (Transact-SQL) - SQL Server (2024)

FAQs

What is the use of hashbytes in SQL Server? ›

hash function - A hash function takes in data and returns back a fixed length block of bits such that any change to the data should result in a different block. HASHBYTES() is actually a function which provides access to several hashing algorithms.

Consider using CHECKSUM or BINARY_CHECKSUM as alternatives to compute a hash value.

You can't - that's the whole idea. A Hash code (like MD5 or SHA) is not encryption: it can't be reversed: Decrypting MD5 and SHA: Why You Can't Do It[^] - this applies to all hashing algorithms.

According to the documentation HASHBYTES RETURN VALUE varbinary (maximum 8000 bytes).

CHECKSUM computes a 32-bit integer value by quite simple-minded XOR-algorithm. hashbytes uses a more sophisticated algorithm, and the value is longer. If you want a unique hash value to use for comparison rather than comparing the base values, you cannot use checksum, because the risk for collisions is too big..

Hashing is commonly used to ensure data integrity. By generating a hash value for an amount of data, such as a file or message, a user can later compare it with the hash value of the received data to verify if any changes or corruption occurred during transmission. Efficient data retrieval.

In short, hashing is the process of using an algorithm to transform large quantities of data into a fixed value. This can be achieved with any volume of data, and the output data size can be any length. This is called a hash value – the hash value is fixed and non-reversible.

This should work with all types and any combinations of types. The difference between BINARY_CHECKSUM an CHECKSUM is that CHECKSUM(a)=CHECKSUM(b) if a=b (or both are NULLs) - so for strings it's charset and collation issue. As manual says - CHECKSUM is intented for building hash indexes.

A hash key is the output from a hashing algorithm, where a specific input value is transformed into a distinct, unique string per input value. The purpose of hash keys in this context is to provide a surrogate key for business keys, composite business keys and business key combinations.

Can hash key be decrypted? ›

No, hashed data cannot be decrypted. Hashing is a one-way process, which means that the original data cannot be obtained from the hash value. It is designed to be irreversible, making it suitable for storing passwords and verifying data integrity.

The MD5 message-digest algorithm is a widely used hash function producing a 128-bit hash value. The value returned by the MD5 function is a binary string of 32 hexadecimal digits, or NULL if the argument was NULL.

The possible values are MD2 , MD4 , MD5 , SHA , SHA1 , SHA2_256 , and SHA2_512 , but only the last two are recommended in SQL Server 2017. input : This is an input variable, column, or expression that needs to be hashed. The data types that are allowed are varchar , nvarchar , and varbinary .

The SQL Server HASHBYTES function is a powerful tool for hashing values using various algorithms like MD5 and SHA. Its significance lies in ensuring data integrity and enabling change detection within databases.

A HASH INDEX is most effective when the data distribution is uniform, and you need to perform a lot of equality comparisons. However, if your queries involve range-based searches or sorting operations, a B-Tree index might be a better choice.

1 Answer. Oracle's SQL Tuning Guide says in the PLAN_TABLE reference: HASH GROUP BY: Operation hashing a set of rows into groups for a query with a GROUP BY clause. SORT GROUP BY: Operation sorting a set of rows into groups for a query with a GROUP BY clause.

They can be used to offer significant performance improvements within data warehousing scenarios, while also offer robust repeatability and consistency in outputs of surrogate key generation, simplifying data migrations and data processing workloads.

A function used to calculate the SHA-256 hash of a data value. The hash will be returned as a hex-encoded string.