Query optimization

query_opt

SELECT
  n.nid as nid
FROM node n
  INNER JOIN content_field_revenue_unit_ref r ON r.nid = n.nid
  INNER JOIN content_type_tax_reporting_units u ON u.nid = r.field_revenue_unit_ref_nid
  LEFT JOIN content_type_tax_sales_report t ON n.nid = t.field_sales_revenue_ref_nid 
    AND t.field_sales_activity_month_value = 12
    AND t.field_sales_activity_year_value = 2012
WHERE n.type = 'tax_revenue_source'
  AND u.field_reporting_unit_status_value = 'A'
  AND n.status = 1
  AND t.nid IS NULL