Build a view of group of Symbols based on their tag.
        
        Parameters
        ----------
        tag : str
            Use '%' to enable SQL's "LIKE" functionality.
        
        Note
        ----
        
        This function is written without SQLAlchemy,
        so it only tested on Postgres.

def build_view_from_tag(self, tag):
        """
        Build a view of group of Symbols based on their tag.
        
        Parameters
        ----------
        tag : str
            Use '%' to enable SQL's "LIKE" functionality.
        
        Note
        ----
        
        This function is written without SQLAlchemy,
        so it only tested on Postgres.

        """
        
        syms = self.search_tag(tag)
        
        names = [sym.name for sym in syms]
        
        subs = ["SELECT indx, '{}' AS symbol, final FROM {}".format(s, s) for s in names]
        
        qry = " UNION ALL ".join(subs)
        
        qry = "CREATE VIEW {} AS {};".format(tag, qry)

        self.ses.execute("DROP VIEW IF EXISTS {};".format(tag))
        self.ses.commit()        
        self.ses.execute(qry)
        self.ses.commit()