## How Can We Efficiently Calculate Hamming Distance on Binary Strings in SQL Databases?

Hamming Distance Computation on Binary Strings in SQL

To efficiently calculate the Hamming distance between binary strings stored in SQL databases, the use of BINARY columns is not recommended due to poor performance. Instead, consider splitting the data into multiple BIGINT columns to represent substrings of the original data.

Following this approach, you can create a custom function like the one provided below:

<code class="sql">CREATE FUNCTION HAMMINGDISTANCE(
  A0 BIGINT, A1 BIGINT, A2 BIGINT, A3 BIGINT, 
  B0 BIGINT, B1 BIGINT, B2 BIGINT, B3 BIGINT
)
RETURNS INT DETERMINISTIC
RETURN 
  BIT_COUNT(A0 ^ B0) +
  BIT_COUNT(A1 ^ B1) +
  BIT_COUNT(A2 ^ B2) +
  BIT_COUNT(A3 ^ B3);</code>

This function operates on 4 BIGINT columns representing substrings of the original 32-byte BINARY column. It computes the Hamming distance of each substring and sums the results.

Using this method significantly improves speed, as demonstrated in testing, where it is over 100 times faster than the approach based on BINARY columns.

Additionally, an alternative approach using substring conversions to compute the Hamming distance on BINARY columns is presented, but it is considered inferior to the BIGINT approach due to its performance considerations.

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