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POhow can I optimize a query with multiple joins (already have indexes)?
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2012-03-12T05:55:17.147
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<pre><code>SELECT citing.article_id as citing, lac_a.year, r.id_when_cited, cited_issue.country, citing.num_citations FROM isi_lac_authored_articles as lac_a JOIN isi_articles citing ON (lac_a.article_id = citing.article_id) JOIN isi_citation_references r ON (citing.article_id = r.article_id) JOIN isi_articles cited ON (cited.id_when_cited = r.id_when_cited) JOIN isi_issues cited_issue ON (cited.issue_id = cited_issue.issue_id); </code></pre> I have indexes on all the fields being JOINED on. Is there anything I can do? My tables are large (some 1 Million records, the references tables has 500 million records, the articles table has 25 Million). This is what EXPLAIN has to say: <pre><code>+----+-------------+-------------+--------+--------------------------------------------------------------------------+---------------------------------------+---------+-------------------------------+---------+-------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------------+--------+--------------------------------------------------------------------------+---------------------------------------+---------+-------------------------------+---------+-------------+ | 1 | SIMPLE | cited_issue | ALL | NULL | NULL | NULL | NULL | 1156856 | | | 1 | SIMPLE | cited | ref | isi_articles_id_when_cited,isi_articles_issue_id | isi_articles_issue_id | 49 | func | 19 | Using where | | 1 | SIMPLE | r | ref | isi_citation_references_article_id,isi_citation_references_id_when_cited | isi_citation_references_id_when_cited | 17 | mimir_dev.cited.id_when_cited | 4 | Using where | | 1 | SIMPLE | lac_a | eq_ref | PRIMARY | PRIMARY | 16 | mimir_dev.r.article_id | 1 | | | 1 | SIMPLE | citing | eq_ref | PRIMARY | PRIMARY | 16 | mimir_dev.r.article_id | 1 | | +----+-------------+-------------+--------+--------------------------------------------------------------------------+---------------------------------------+---------+-------------------------------+---------+-------------+ 5 rows in set (0.07 sec) </code></pre>
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<mysql><optimization>
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how can I optimize a query with multiple joins (already have indexes)?
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