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 <= '1284107770' AND a.id='1' AND b.id=a.cid GROUP BY a.id<br />Unknown column 'a.enviado_por' in 'on clause'