Language reference

HASHBYTES (SQL Server's digest by algorithm name, in hex)

Syntax

HASHBYTES(<algorithm>, <string>)

π customer_id, HASHBYTES('SHA2_256', email) → digest (Customers)

Description

HASHBYTES is SQL Server's hash function, which names its algorithm first. It gives the same digest as the function for that algorithm: HASHBYTES('MD5', s) is MD5(s).

Technical Description

HASHBYTES(algorithm: STRING, s: STRING) → STRING. The algorithm is MD5, SHA, SHA1, SHA2_256 or SHA2_512, in any case; another is an error naming these. The digest is of the UTF-8 bytes of s, in lowercase hex. A NULL algorithm or s returns NULL. PURE, DETERMINISTIC.

Examples

A SHA-256 digest of each customer's email:

π customer_id, HASHBYTES('SHA2_256', email) → digest (Customers)

PROJECT customer_id, HASHBYTES('SHA2_256', email) -> digest (Customers)

Pushdown

It runs in the engine. SQL Server's own HASHBYTES hashes an NVARCHAR as UTF-16 and returns bytes, so it would answer differently.

SQL names

SQL Server's HASHBYTES, which returns VARBINARY; here the digest is hex text, as LOWER(CONVERT(VARCHAR(128), HASHBYTES(a, s), 2)) gives it there for a VARCHAR in a UTF-8 collation. MD2 and MD4 are not taken.