¿Cómo extraer de la BD dos veces en la misma consulta?

[gnzsoloyo]

Estás escribiendo mal la sentencia. Si usas INNER JOIN, la sintaxis es así:

Código MySQL:

SELECT 
    A.id_answer, 
    A.answer, 
    A.id_questions, 
    A.id_users, 
    A.id_friend, 
    A.datetime,
    A.statement,
    Q.id_question, 
    Q.question, 
    Q.id_typequestions,
    TQ.id_typequestion, 
    TQ.typequestion,
    U.id_user Uid, 
    U.id_twitter Uidtw, 
    U.name Un, 
    U.screen_name Uscr, 
    U.image Uimg,
    US.id_twitter USidtw, 
    US.name USn, 
    US.image USimg 
FROM 
    answers A
    INNER JOIN questions Q ON A.id_questions=Q.id_question
    INNER JOIN  typequestions TQ ON Q.id_typequestions=TQ.id_typequestion
    INNER JOIN  users U ON A.id_users=U.id_user
    INNER JOIN  users US ON A.id_friend=US.id_twitter
WHERE 
    A.id_users=14 OR 
    A.id_friend=ANY(SELECT id_twitter FROM users WHERE id_user=14)