[5.1 数据定义](5.1%E6%95%B0%E6%8D%AE%E5%AE%9A%E4%B9%89.md) [5.2 常见问题答疑](5.2%E6%B3%8A%E9%93%BE%E5%B8%B8%E8%A7%81%E9%97%AE%E9%A2%98%E7%AD%94%E7%96%91.md)