cursor.execute在django中没有返回任何内容，但它适用于mysql

Question

所以我想使用cursor.execute在Django中运行查询：

def get_user_history(user_id):
with connection.cursor() as cursor:
    cursor.execute("""
        SET @user_id = %s;
        SELECT * FROM (
            SELECT channel_id, NULL as article_id, NULL as comment_id,
                NULL as friend_id, NULL as followed_channel_id,
                NULL as liked_article_id, created_at
                FROM channel WHERE user_id = @user_id
            UNION ALL
            SELECT channel_id, article_id, NULL as comment_id,
                NULL as friend_id, NULL as followed_channel_id,
                NULL as liked_article_id, created_at
                FROM article WHERE channel_id in
                    (SELECT channel_id from channel where user_id = @user_id)
            UNION ALL
            SELECT NULL as channel_id, article_id, comment_id,
                NULL as friend_id, NULL as followed_channel_id,
                NULL as liked_article_id, created_at
                FROM comment WHERE user_id = @user_id
            UNION ALL
            SELECT NULL as channel_id, NULL as article_id, NULL as comment_id,
                friend_id, NULL as followed_channel_id,
                NULL as liked_article_id, created_at
                FROM user_friends WHERE user_id = @user_id
            UNION ALL
            SELECT NULL as channel_id, NULL as article_id, NULL as comment_id,
                NULL as friend_id, channel_id as followed_channel_id,
                NULL as liked_article_id, created_at
                FROM user_follows_channel WHERE user_id = @user_id
            UNION ALL
            SELECT NULL as channel_id, NULL as article_id, NULL as comment_id,
                NULL as friend_id, NULL as followed_channel_id,
                article_id as liked_article_id, created_at
                FROM user_likes_article WHERE user_id = @user_id
            ) T1
        ORDER BY created_at;
        """, [user_id])
    if cursor.fetchall():
        return dictfetchall(cursor)
    else:
        return {'error': 'history is empty'}

但它返回一个空对象[]，但是当我在mariaDB中使用

运行完全相同的sql代码时

mysql -u root -p    

它会返回我想要的正确结果：

+------------+------------+------------+-----------+---------------------+------------------+---------------------+

    | channel_id | article_id | comment_id | friend_id | followed_channel_id | liked_article_id | created_at          |
    +------------+------------+------------+-----------+---------------------+------------------+---------------------+
    |          3 |       NULL |       NULL |      NULL |                NULL |             NULL | 2017-12-04 01:44:35 |
    |          3 |          5 |       NULL |      NULL |                NULL |             NULL | 2017-12-04 15:40:23 |
    |          3 |          6 |       NULL |      NULL |                NULL |             NULL | 2017-12-04 16:34:57 |
    +------------+------------+------------+-----------+---------------------+------------------+---------------------+

我完全难过了。