Query:
SELECT c.title AS title , c.introtext AS body , c.state AS state , c.created AS created , c.created_by AS
You preform the join between jos_categories and jos_categories AS jc:
jos_categories
jos_categories AS jc
jos_content AS c, jos_categories INNER JOIN jos_categories AS jc ON c.sectionid = jc.section
but c is jos_content...
c
jos_content