关于数据表中字段属性“NULL”的理解与使用

THE UNDERSTANDING AND USING OF“NULL”WHICH IS THE PROPERTY OF THE FIELDS IN THE DATABASE TABLE

本文针对关系数据库表中字段属性“NULL”的设置、赋值及其有关编程处理方法进行了讨论和分析 ,并给出了一些明确的结论和使用建议。这些结论和建议对于数据库维护及有关软件开发的编程和测试人员 ,具有较高的使用和参考价值。

This paper discusses and analyses the setting,evaluate and ways of the relating programming about“NULL”,which is the property of filed in the relational database table.Moreover,this paper gives some specific conclusions and advice.These conclusions and advice take on upper values of using and reference for the database maintenance and the relating software developing.