De-duplicating many-to-many relationships in MySQL lookup table -

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i've inherited database includes lookup table find other patents related given patent.

so looks 

╔════╦═══════════╦════════════╗ ║ id ║ patent_id ║ related_id ║ ╠════╬═══════════╬════════════╣ ║ 1  ║     1     ║     2      ║ ║ 2  ║     1     ║     3      ║ ║ 3  ║     2     ║     1      ║ ║ 4  ║     2     ║     3      ║ ║ 5  ║     3     ║     2      ║ ╚════╩═══════════╩════════════╝

and want filter out reciprocal relationships. 1->2 , 2->1 same purposes want 1->2.

i don't need make edit in table, need query returns list of unique relationships, , while i'm sure it's simple i've been banging head against keyboard far long.

here clever query can try using. general strategy identify unwanted duplicate records , subtract them away entire set.

select t.id, t.patent_id, t.related_id t left join (     select t1.patent_id t1_patent_id, t1.related_id t1_related_id     t t1 left join t t2     on t1.related_id = t2.patent_id     t1.patent_id = t2.related_id , t1.patent_id > t1.related_id ) t3 on t.patent_id = t3.t1_patent_id , t.related_id = t3.t1_related_id t3.t1_patent_id null

here inner temporary table generated query. can convince applying logic in where clause select correct records. non-duplicate records characterized t1.patent_id != t2.related_id, , these records retained. in case of duplicates (t1.patent_id = t2.related_id), record chosen each pair of duplicates 1 patent_id < related_id, requested in question.

╔════╦══════════════╦═══════════════╦══════════════╦═══════════════╗   ║ id ║ t1.patent_id ║ t1.related_id ║ t2.patent_id ║ t2.related_id ║ ╠════╬══════════════╬═══════════════╬══════════════╬═══════════════╣ ║ 1  ║      1       ║       2       ║      2       ║       1       ║ * duplicate ║ 1  ║      1       ║       2       ║      2       ║       3       ║ ║ 2  ║      1       ║       3       ║      3       ║       2       ║ ║ 3  ║      2       ║       1       ║      1       ║       2       ║ * duplicate ║ 3  ║      2       ║       1       ║      1       ║       3       ║ ║ 4  ║      2       ║       3       ║      3       ║       2       ║ * duplicate ║ 5  ║      3       ║       2       ║      2       ║       1       ║ ║ 5  ║      3       ║       2       ║      2       ║       3       ║ * duplicate ╚════╩══════════════╩═══════════════╩══════════════╩═══════════════╝

click link below running example of query.

sqlfiddle


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