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POMySQL: an efficient binary value comparison
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15791497
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2013-04-03T15:23:04.843
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My table has 8 VARCHAR fields of binary strings of 64bits each one. My goal is to get <a href="http://en.wikipedia.org/wiki/Hamming_distance" rel="nofollow">Hamming distance</a> for each register. I was doing it with the next query : <pre><code>SELECT BIT_COUNT(CONV(fp.bin_str0, 2, 10 ) ^ CONV('0000000001101111000000000101011100000000001010100000000001111101', 2, 10 )) + BIT_COUNT(CONV(fp.bin_str1, 2, 10 ) ^ CONV('0000000010110001000000001000000000000000011000010000000011110100', 2, 10 )) + BIT_COUNT(CONV(fp.bin_str2, 2, 10 ) ^ CONV('0000000010010100000000000010101100000000110001000000000011100100', 2, 10 )) + BIT_COUNT(CONV(fp.bin_str3, 2, 10 ) ^ CONV('0000000011101011000000000001110000000000101100010000000000011001', 2, 10 )) + BIT_COUNT(CONV(fp.bin_str4, 2, 10 ) ^ CONV('0000000000010000000000000011010100000000111011100000000001001101', 2, 10 )) + BIT_COUNT(CONV(fp.bin_str5, 2, 10 ) ^ CONV('0000000000101111000000000110101000000000000010100000000000101101', 2, 10 )) + BIT_COUNT(CONV(fp.bin_str6, 2, 10 ) ^ CONV('0000000000011000000000000101011000000000001010000000000000001011', 2, 10 )) + BIT_COUNT(CONV(fp.bin_str7, 2, 10 ) ^ CONV('0000000000101011000000000011100100000000000100000000000000111010', 2, 10 )) from mytable fp </code></pre> So this query is extremely slow. There are some reasons: mytable has 3M registers and the field <code>fp.bin_stri</code> is of VARCHAR type. As MySQL has BINARY type, can I execute the same query over <code>fp.bin_stri</code> of BINARY type? An how? I'm confused because, when I have changed <code>fp.bin_stri</code> to BINARY, the data of this field has appeared as BLOB and now I don't know how the query should look like. Should it use <code>CONV</code>? 
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<mysql><types><binary>
Title
MySQL: an efficient binary value comparison
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