SELECT a.*,b.nombre AS categoria,c.nombre,c.web FROM blog_post AS a,blog_categorias AS b LEFT JOIN blog_usuarios AS c ON c.uid=a.enviado_por WHERE a.fecha <= '1216850216' AND a.id='147' AND b.id=a.cid GROUP BY a.id<br />Unknown column 'a.enviado_por' in 'on clause'