Error SELECT expo.tema_sp AS tema, expo.descrip_sp AS descrip, expo.id AS item,o.doc_img, o.titulo
      FROM tema_foto AS expo 
	  LEFT JOIN obra_tema AS ot ON ot.tema=expo.id
	  LEFT JOIN obra AS o ON o.id=ot.obra
      WHERE expo.tema_sp <> '' AND expo.descrip_sp <> ''
	  ORDER BY expo.id  DESC LIMIT 1