SHA2 Function

Overview

The SHA2 function is a unified interface for the SHA-2 family of hash algorithms, allowing selection of a specific SHA-2 variant (SHA-224, SHA-256, SHA-384, SHA-512) via the bit_length parameter. The SHA-2 family of algorithms can map arbitrary-length data to fixed-length hash values, outputting a hexadecimal string whose length depends on the chosen variant.

Syntax

sha2(expr, bit_length)

Parameters

• expr: The input data for which to compute the hash value. Supports STRING, VARCHAR, CHAR, and BINARY types.
• bit_length: Integer type (INT), specifying which SHA-2 variant to use. Supports the following values:
  • 0 — equivalent to 256, uses the SHA-256 algorithm
  • 224 — uses the SHA-224 algorithm, outputs a 56-character hexadecimal string
  • 256 — uses the SHA-256 algorithm, outputs a 64-character hexadecimal string
  • 384 — uses the SHA-384 algorithm, outputs a 96-character hexadecimal string
  • 512 — uses the SHA-512 algorithm, outputs a 128-character hexadecimal string

Return Result

Returns a STRING type value representing the computed hexadecimal hash string. The output length depends on the bit_length parameter:

Examples

1. Compute the hash value using SHA-256 (bit_length=256):

   SELECT sha2('abc', 256) AS res; +------------------------------------------------------------------+ | res | +------------------------------------------------------------------+ | ba7816bf8f01cfea414140de5dae2223b00361a396177a9cb410ff61f20015ad | +------------------------------------------------------------------+

2. Compute the hash value using SHA-224 (bit_length=224):

   SELECT sha2('abc', 224) AS res; +----------------------------------------------------------+ | res | +----------------------------------------------------------+ | 23097d223405d8228642a477bda255b32aadbce4bda0b3f7e36c9da7 | +----------------------------------------------------------+

3. Compute the hash value using SHA-384 (bit_length=384):

   SELECT sha2('abc', 384) AS res; +--------------------------------------------------------------------------------------------------+ | res | +--------------------------------------------------------------------------------------------------+ | cb00753f45a35e8bb5a03d699ac65007272c32ab0eded1631a8b605a43ff5bed8086072ba1e7cc2358baeca134c825a7 | +--------------------------------------------------------------------------------------------------+

4. Compute the hash value using SHA-512 (bit_length=512):

   SELECT sha2('abc', 512) AS res; +----------------------------------------------------------------------------------------------------------------------------------+ | res | +----------------------------------------------------------------------------------------------------------------------------------+ | ddaf35a193617abacc417349ae20413112e6fa4e89a97ea20a9eeee64b55d39a2192992a274fc1a836ba3c23a3feebbd454d4423643ce80e2a9ac94fa54ca49f | +----------------------------------------------------------------------------------------------------------------------------------+

5. Using bit_length=0 (equivalent to SHA-256):

   SELECT sha2('abc', 0) AS res; +------------------------------------------------------------------+ | res | +------------------------------------------------------------------+ | ba7816bf8f01cfea414140de5dae2223b00361a396177a9cb410ff61f20015ad | +------------------------------------------------------------------+

6. When the input is NULL:

   SELECT sha2(NULL, 256) AS res; +------+ | res | +------+ | NULL | +------+

Notes

• When the input parameter expr is NULL, the result is NULL.
• When bit_length is 0, it is equivalent to bit_length being 256, using the SHA-256 algorithm.
• When bit_length is not one of 0, 224, 256, 384, or 512, the function will throw an error.
• SHA-2 series hash values are irreversible, meaning the original data cannot be derived from the hash value.
• If you only need to use a fixed SHA-2 variant, you can also use the corresponding standalone functions directly: sha224(), sha256(), sha384(), sha512().