def get_tablaturecomments(self, tablature_id):
        """
        Get comments to a tablature
        """
        keys_on = "PRAGMA foreign_keys = ON"

        query = "SELECT * FROM comments WHERE tablature_id = ?"
        pvalue = (tablature_id,)

        if not self.contains_tablature(tablature_id):
            return None

        con = sqlite3.connect(self.database_name)
        with con:
            con.row_factory = sqlite3.Row
            cur = con.cursor()
            cur.execute(keys_on)

            cur.execute(query, pvalue)

            rows = cur.fetchall()
            if rows == []:
                return None

            comments = []
            for row in rows:
                comments.append(CommentModel.create(row))
            return comments
    def get_comments_by_user(self, user_nickname):
        """
        Returns comments.
        If comments doesn't exist return "None".
        """

        keys_on = "PRAGMA foreign_keys = ON"
        query = "SELECT * FROM comments WHERE user_nickname = ?"
        pvalue = (user_nickname,)

        # connects (and creates if necessary) to the database. gets a connection object
        con = sqlite3.connect(self.database_name)
        with con:
            con.row_factory = sqlite3.Row
            cur = con.cursor()
            cur.execute(keys_on)
            # execute the statement
            cur.execute(query, pvalue)
            # just one result possible
            rows = cur.fetchall()
            comments = []
            if rows is None:
                return None
            else:
                # print row.keys()
                for row in rows:
                    comments.appdend(CommentModel.create(row))
            return comments
    def get_comment(self, comment_id):
        """
        Returns the comment.
        If comment doesn't exist return "None".
        """

        keys_on = "PRAGMA foreign_keys = ON"
        query = "SELECT * FROM comments WHERE comment_id = ?"
        pvalue = (comment_id,)

        # connects (and creates if necessary) to the database. gets a connection object
        con = sqlite3.connect(self.database_name)
        with con:
            con.row_factory = sqlite3.Row
            cur = con.cursor()
            cur.execute(keys_on)
            # execute the statement
            cur.execute(query, pvalue)
            # just one result possible
            row = cur.fetchone()
            if row is None:
                return None
            else:
                # print row.keys()

                return CommentModel.create(row)
    def get_tablaturecomments(self, tablature_id):
        '''
        Get comments to a tablature
        '''
        keys_on = 'PRAGMA foreign_keys = ON'

        query = 'SELECT * FROM comments WHERE tablature_id = ?'
        pvalue = (tablature_id, )

        if not self.contains_tablature(tablature_id):
            return None

        con = sqlite3.connect(self.database_name)
        with con:
            con.row_factory = sqlite3.Row
            cur = con.cursor()
            cur.execute(keys_on)

            cur.execute(query, pvalue)

            rows = cur.fetchall()
            if rows == []:
                return None

            comments = []
            for row in rows:
                comments.append(CommentModel.create(row))
            return comments
    def get_comments_by_user(self, user_nickname):
        '''
        Returns comments.
        If comments doesn't exist return "None".
        '''

        keys_on = 'PRAGMA foreign_keys = ON'
        query = 'SELECT * FROM comments WHERE user_nickname = ?'
        pvalue = (user_nickname, )

        #connects (and creates if necessary) to the database. gets a connection object
        con = sqlite3.connect(self.database_name)
        with con:
            con.row_factory = sqlite3.Row
            cur = con.cursor()
            cur.execute(keys_on)
            #execute the statement
            cur.execute(query, pvalue)
            #just one result possible
            rows = cur.fetchall()
            comments = []
            if rows is None:
                return None
            else:
                #print row.keys()
                for row in rows:
                    comments.appdend(CommentModel.create(row))
            return comments
    def get_comment(self, comment_id):
        '''
        Returns the comment.
        If comment doesn't exist return "None".
        '''

        keys_on = 'PRAGMA foreign_keys = ON'
        query = 'SELECT * FROM comments WHERE comment_id = ?'
        pvalue = (comment_id, )

        #connects (and creates if necessary) to the database. gets a connection object
        con = sqlite3.connect(self.database_name)
        with con:
            con.row_factory = sqlite3.Row
            cur = con.cursor()
            cur.execute(keys_on)
            #execute the statement
            cur.execute(query, pvalue)
            #just one result possible
            row = cur.fetchone()
            if row is None:
                return None
            else:
                #print row.keys()

                return CommentModel.create(row)