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POEfficiency in SQL query
 

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  1. POEfficiency in SQL query
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    <hr> <p>I have created a search functionality to my cake application. It is built from multiple select boxes in which you can select data, then it cycles through the selected options and implements them to the SQL syntax.</p> <p>Basically this is how the function looks like:</p> <pre><code>$selectedFilters = $this-&gt;data; $selectSQL = 'SELECT agencies.agency, agencies.website_url, agencies.status, agencies.size, agencies.id, OfficeData.id, ContactData.name, ContactData.surname, ContactData.job_title, ContactData.email, ContactData.mobile, OfficeCountryData.country FROM agencies LEFT JOIN (SELECT agencies_industries.agency_id, agencies_industries.industry_id FROM agencies_industries) AS IndustryData ON agencies.id = IndustryData.agency_id LEFT JOIN (SELECT agencies_professions.agency_id, agencies_professions.profession_id FROM agencies_professions) AS ProfessionData ON agencies.id = ProfessionData.agency_id LEFT JOIN (SELECT agencies_sectors.agency_id, agencies_sectors.sector_id FROM agencies_sectors) AS SectorData ON agencies.id = SectorData.agency_id LEFT JOIN (SELECT agencies_seniorities.agency_id, agencies_seniorities.seniority_id FROM agencies_seniorities) AS SeniorityData ON agencies.id = SeniorityData.agency_id LEFT JOIN (SELECT agencies_zones.agency_id, agencies_zones.zone_id FROM agencies_zones) AS ZonesData ON agencies.id = ZonesData.agency_id LEFT JOIN (SELECT agencies_countries.agency_id, agencies_countries.country_id FROM agencies_countries) AS CountryData ON agencies.id = CountryData.agency_id LEFT JOIN (SELECT agencies_regions.agency_id, agencies_regions.region_id FROM agencies_regions) AS RegionData ON agencies.id = RegionData.agency_id LEFT JOIN (SELECT agencies_cities.agency_id, agencies_cities.city_id FROM agencies_cities) AS CityData ON agencies.id = CityData.agency_id LEFT JOIN (SELECT agencies_specialisms.agency_id, agencies_specialisms.specialism_id FROM agencies_specialisms) AS SpecialismData ON agencies.id = SpecialismData.agency_id LEFT JOIN (SELECT offices.id, offices.agency_id, offices.hq FROM offices WHERE offices.hq = "1") AS OfficeData ON agencies.id = OfficeData.agency_id LEFT JOIN (SELECT countries.id, countries.country FROM countries) AS OfficeCountryData ON OfficeData.hq = OfficeCountryData.id LEFT JOIN (SELECT contacts.name, contacts.surname, contacts.agency_id, contacts.job_title, contacts.email, contacts.mobile FROM contacts) AS ContactData ON agencies.id = ContactData.agency_id '; $whereSQL = ' WHERE 1 = 1 '; foreach($selectedFilters as $key) foreach($key as $name=&gt;$value){ if(is_array($key)) foreach($key as $key=&gt;$value){ $i = 0; $connector = 'AND'; if(is_array($value)){ foreach($value as $value){ if($i &gt; 0) $connector = 'OR'; $i++; switch($key){ case 'Profession': $whereSQL .= $connector.' ProfessionData.profession_id = ' . $value . ' '; break; case 'Specialism': $whereSQL .= $connector.' SpecialismData.specialism_id = ' . $value . ' '; break; case 'SubSpecialism': $whereSQL .= ''; //$whereSQL .= $connector.' SubData.sub_specialism_id = ' . $value . ' '; break; case 'Seniority': $whereSQL .= $connector.' SeniorityData.seniority_id = ' . $value . ' '; break; case 'Industry': $whereSQL .= $connector.' IndustryData.industry_id = ' . $value . ' '; break; case 'Zone': $whereSQL .= $connector.' ZonesData.zone_id = ' . $value . ' '; break; case 'Country': $whereSQL .= $connector.' CountryData.country_id = ' . $value . ' '; break; case 'Region': $whereSQL .= $connector.' RegionData.region_id = ' . $value . ' '; break; case 'City': $whereSQL .= $connector.' CityData.city_id = ' . $value . ' '; break; case 'Sector': $whereSQL .= $connector.' SectorData.sector_id = ' . $value . ' '; break; case 'status': $whereSQL .= $connector.' agencies.status = "' . $value . '" '; break; case 'size': $whereSQL .= $connector.' agencies.size = "' . $value . '" '; break; } } } else if(!isBlank($value) &amp;&amp; $key != 'Search') $whereSQL .= $connector.' agencies.'.$key.' = "'.$value.'" '; } } $groupBySQL = 'GROUP BY agencies.id ORDER BY agencies.id ASC'; $resultAgencies = $this-&gt;Agency-&gt;query($selectSQL . $whereSQL . $groupBySQL); $this-&gt;set(compact('resultAgencies')); </code></pre> <p>The problem I encountered with my search is that it works really slow. This happens because of using too many <code>LEFT JOIN</code> commands. Every <code>LEFT JOIN</code> selects data from distinct tables and gathers them all creating another table. Then the data is displayed.</p> <p>I need someone to give me a hint how to do this not using so many <code>LEFT JOINs</code>.</p> <p>Cheers.</p>
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    1. COIt's not the JOINS that is killing your query but the amount of subqueries! Why join on a subquery and not on the table?
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