private void generateSelectExpression(MySqlSelectQueryBlock stmt, MVContext context) {
        List<SQLSelectItem> selectList = stmt.getSelectList();
        if(selectList != null && selectList.size() > 0) {
            String sql = "insert into mview_expression(type, mview_id, expression, expr_order) values('select', ?, ?, ?)";
            PreparedStatement pstmt = null;
            try {
                pstmt = dbCon.prepareStatement(sql);
                for(int seq=0; seq < selectList.size(); seq ++) {
                    pstmt.setLong(1, context.getMview().getId());
                    pstmt.setString(2, selectList.get(seq).toString());
                    pstmt.setInt(3, seq);
                    pstmt.executeUpdate();
                }
            } catch (SQLException e) {
                logger.error("Error when generating select expression", e);
                throw new TransactionException(getTransactionID(), e);
            } finally {
                try {
                    pstmt.close();
                } catch (Exception ignore) {
                }
            }
        }
    }