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POMysql query performance is slow, need help in optimization
 

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    <p>I have 4 tables: shipments (200K records), stores (45 records), product_stores (8K records), districts (698 records). The following query takes very long time to excute (12 seconds):</p> <pre><code>SELECT `s`. * , `p`.`productCode` , `p`.`productName` , `st`.`name` AS `storeName` , `d`.`name` AS `districtName` FROM `shipments` AS `s` JOIN `product_stores` AS `p` ON s.productStoreId = p.id JOIN `stores` AS `st` ON s.storeId = st.id LEFT JOIN `districts` AS `d` ON s.districtId = d.id WHERE (s.storeId IN (1, 2, 3, 4, 6, 9, 14, 16, 22, 26, 30)) GROUP BY `s`.`id` ORDER BY `s`.`id` DESC LIMIT 100 </code></pre> <p>EXPLAIN query return the following result:</p> <pre><code>id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE st ALL PRIMARY NULL NULL NULL 45 Using where; Using temporary; Using filesort 1 SIMPLE s ref fk_shipments_stores1_idx,fk_shipments_product_stor... fk_shipments_stores1_idx 4 st.id 482 1 SIMPLE p eq_ref PRIMARY PRIMARY 4 s.productStoreId 1 1 SIMPLE d eq_ref PRIMARY PRIMARY 4 s.districtId 1 </code></pre> <ol> <li>I don't know why mysql must Using temporary; Using filesort in this case</li> <li>Why mysql not start select from shipments? then join store. it start select from store then join shipments? I try to run the EXPLAIN and sometime mysql start select from table product_stores</li> <li>Please help me to optimize the table, indexes...to improve performance.</li> </ol> <p>(I'm using mysql 5.0.95)</p> <p>This is the table structures:</p>
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    1. USKevin
    1. USKevin
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      1. USBen Swinburne
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    1. COPlease change your question header to something useful.
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