数据库null区别的相关内容

阿里云文档 2025-10-21

PSL4和PSL5两种存储类型有什么区别,如何使用

PSL4和PSL5是PolarDB为不同业务场景所提供的存储类型，两者在价格、数据可靠性及性能方面均存在部分差异。本文为您介绍这两种存储类型的区别，帮助您决策如何选择。

阿里云文档 2025-04-28

RDS倚天版和标准版的区别

为了进一步降低用户成本，云数据库RDS推出倚天版实例和标准版实例，ARM实例已被纳入倚天版实例。

阿里云文档 2025-02-20

逻辑备份、物理备份与快照的区别

本文介绍逻辑备份、物理备份与快照的区别，以及使用数据灾备控制台创建备份计划时如何选择备份方式。

阿里云文档 2024-02-06

云数据库RDS MariaDB存储类型的区别及选购建议

云数据库RDS MariaDB提供了ESSD云盘、SSD云盘两种存储类型，本文介绍这两种存储类型的基本信息及选购建议。

文章 2023-09-22 来自：开发者社区

MySQL数据库的表中 NULL 和空值到底有什么区别呢？

个人主页极客小俊✍ 作者简介：web开发者、设计师、技术分享博主希望大家多多支持一下, 我们一起进步！如果文章对你有帮助的话，欢迎评论点赞收藏加关注浅谈 NULL 和空值的区别 NULL也就是在字段中存储NULL值空字符串值也就是字段中存储空字符('') 我们来通过测试来看看他们彼此的区别: 1、占用空间区别 mysql> select...

阿里云文档 2023-09-03

触发器和规则系统规则vs触发器有哪些区别？_云原生数据库PolarDB PostgreSQL版（兼容Oracle）_云原生数据库 PolarDB(PolarDB)

许多触发器可以干的事情同样也可以用PostgreSQL规则系统来实现。目前不能用规则来实现的东西之一是某些约束，特别是外键。可以放置一个合格的规则在一列上，这个规则在列的值没有出现在另一个表中时把命令重写成NOTHING。但是这样做数据就会被不声不响地丢弃，因此也不是一个好主意。如果要求检查值的有效性，并且在出现无效值的情况下应该生成一个错误消息，这种需求就必须要用触发器来完成。

问答 2022-04-15 来自：开发者社区

数据库中，NULL与空值有什么区别

创建数据库的时候，对某个字段定义了 NOT NULL，但是，在写入数据的时候，空字符串''竟然也能写入成功。有人能给我解释一下 NULL 和 NOT NULL 到底是什么意思呢？

共有7条

< 1 >

跳转至： GO

更新时间 2024-07-22 09:35:58

本页面内关键词为智能算法引擎基于机器学习所生成，如有任何问题，可在页面下方点击"联系我们"与我们沟通。

数据库更多区别相关

数据库您可能感兴趣

产品推荐

{"optioninfo":{"dynamic":"ture","static":"true"},"simplifiedDisplay":"newEdition","newCard":[{"ifIcon":"img","link":"https://img.alicdn.com/tfs/TB1XY8hGYr1gK0jSZFDXXb9yVXa-1740-328.png","icon":"","iconImg":"https://img.alicdn.com/tfs/TB1nmXJn7cx_u4jSZFlXXXnUFXa-200-200.png","contentLink":"https://www.aliyun.com/product/dbaudit","title":"数据库审计","des":"满足等保2.0二级和三级 “安全审计”合规要求的同时，智能解析数据库通信流量，细粒度审计数据库访问行为，通过对数据库全量行为的审计溯源、危险攻击的实时告警、风险语句的智能预警，提供数据库资产最安全的监控保障。","link1":"https://yundun.console.aliyun.com/?p=sddp#/audit/analysis/alarm/auditFirst/cn-zhangjiakou","btn1":"产品控制台","link2":"https://common-buy.aliyun.com/?commodityCode=sddp_pre&request=%7B%22ord_time%22:%221:Month%22,%22order_num%22:1,%22region%22:%22cn-zhangjiakou%22,%22type%22:%22normal%22,%22sddp_version%22:%22version_dengbao%22,%22audit_subscription_version%22:%220%22,%22logStorage_subscription%22:%221%22,%22logStorage%22:2%7D&regionId=cn-zhangjiakou","btn2":"立即购买","btn3":"产品文档","link3":"https://help.aliyun.com/product/52432.html?spm=5176.139959.J_5253785160.5.42de77d7KNxtZZ","infoGroup":[{"infoName":"精选推荐","infoContent":{"firstContentName":"包年享85折优惠","firstContentLink":"https://common-buy.aliyun.com/?commodityCode=sddp_pre&request=%7B%22ord_time%22:%221:Month%22,%22order_num%22:1,%22region%22:%22cn-zhangjiakou%22,%22type%22:%22normal%22,%22sddp_version%22:%22version_dengbao%22,%22audit_subscription_version%22:%220%22,%22logStorage_subscription%22:%221%22,%22logStorage%22:2%7D&regionId=cn-zhangjiakou","lastContentLink":"","lastContentName":""}},{"infoName":"用户指南","infoContent":{"firstContentName":"产品快速入门","lastContentName":"不同版本功能对比","firstContentLink":"https://help.aliyun.com/zh/dsc/data-security-center/user-guide/security-audit/","lastContentLink":"https://help.aliyun.com/zh/dsc/data-security-center/product-overview/difference-between-different-dsc-editions"}}]}],"card":[],"search":[],"infoCard":[{"bannerUrl":"https://img.alicdn.com/tfs/TB1Xf81a3gP7K4jSZFqXXamhVXa-5169-974.jpg","bannerTitle":"数据库审计","bannerContent":"满足等保2.0二级和三级 “安全审计”合规要求的同时，智能解析数据库通信流量，细粒度审计数据库访问行为，通过对数据库全量行为的审计溯源、危险攻击的实时告警、风险语句的智能预警，提供数据库资产最安全的监控保障。","liveButtonName":"查看详情","liveButtonLink":"https://www.aliyun.com/product/dbaudit?spm=5176.21213303.8115314850.1.faf453c9I9EKNe&scm=20140722.S_card@@%E5%8D%A1%E7%89%87@@1796._.ID_card@@%E5%8D%A1%E7%89%87@@1796-RL_%E6%95%B0%E6%8D%AE%E5%BA%93%E5%AE%A1%E8%AE%A1-OR_ser-V_2-P0_0","contentTitle":"满足等保2.0’安全审计‘的合规要求","homePageLink":"https://page.aliyun.com/form/act803688306/index.htm","homePageName":"7天试用","linkGroup":[{"linkContent":"发布包大小极致优化，节省流量和存储。"},{"linkContent":"服务迭代不再受发版限制，快速发布，快速迭代。"},{"linkContent":"业务开发效率更加优秀，一次开发，多端运行。"}]}],"title":{"mainTitle":"数据库审计","subtitle":"满足等保2.0二级和三级 “安全审计”合规要求的同时，智能解析数据库通信流量，细粒度审计数据库访问行为，通过对数据库全量行为的审计溯源、危险攻击的实时告警、风险语句的智能预警，提供数据库资产最安全的监控保障。","linkUrl":"https://www.aliyun.com/product/dbaudit?spm=5176.21213303.8115314850.1.faf453c9I9EKNe&scm=20140722.S_card@@%E5%8D%A1%E7%89%87@@1796._.ID_card@@%E5%8D%A1%E7%89%87@@1796-RL_%E6%95%B0%E6%8D%AE%E5%BA%93%E5%AE%A1%E8%AE%A1-OR_ser-V_2-P0_0","btnText":"查看详情"},"visual":{"topbg":"https://img.alicdn.com/tfs/TB1bQuBIYH1gK0jSZFwXXc7aXXa-3840-740.gif","icon":"","textColor":"dark"},"dataList":[{"summary":"啦啦啦","author":"wuwu","linksUrl":"#"}],"sceneCard":[],"txt":[]}

{"$env":{"JSON":{}},"$page":{"env":"production"},"$context":{"optioninfo":{"dynamic":"ture","static":"true"},"simplifiedDisplay":"newEdition","newCard":[{"ifIcon":"img","link":"https://img.alicdn.com/tfs/TB1XY8hGYr1gK0jSZFDXXb9yVXa-1740-328.png","icon":"","iconImg":"https://img.alicdn.com/tfs/TB1nmXJn7cx_u4jSZFlXXXnUFXa-200-200.png","contentLink":"https://www.aliyun.com/product/dbaudit","title":"数据库审计","des":"满足等保2.0二级和三级 “安全审计”合规要求的同时，智能解析数据库通信流量，细粒度审计数据库访问行为，通过对数据库全量行为的审计溯源、危险攻击的实时告警、风险语句的智能预警，提供数据库资产最安全的监控保障。","link1":"https://yundun.console.aliyun.com/?p=sddp#/audit/analysis/alarm/auditFirst/cn-zhangjiakou","btn1":"产品控制台","link2":"https://common-buy.aliyun.com/?commodityCode=sddp_pre&request=%7B%22ord_time%22:%221:Month%22,%22order_num%22:1,%22region%22:%22cn-zhangjiakou%22,%22type%22:%22normal%22,%22sddp_version%22:%22version_dengbao%22,%22audit_subscription_version%22:%220%22,%22logStorage_subscription%22:%221%22,%22logStorage%22:2%7D&regionId=cn-zhangjiakou","btn2":"立即购买","btn3":"产品文档","link3":"https://help.aliyun.com/product/52432.html?spm=5176.139959.J_5253785160.5.42de77d7KNxtZZ","infoGroup":[{"infoName":"精选推荐","infoContent":{"firstContentName":"包年享85折优惠","firstContentLink":"https://common-buy.aliyun.com/?commodityCode=sddp_pre&request=%7B%22ord_time%22:%221:Month%22,%22order_num%22:1,%22region%22:%22cn-zhangjiakou%22,%22type%22:%22normal%22,%22sddp_version%22:%22version_dengbao%22,%22audit_subscription_version%22:%220%22,%22logStorage_subscription%22:%221%22,%22logStorage%22:2%7D&regionId=cn-zhangjiakou","lastContentLink":"","lastContentName":""}},{"infoName":"用户指南","infoContent":{"firstContentName":"产品快速入门","lastContentName":"不同版本功能对比","firstContentLink":"https://help.aliyun.com/zh/dsc/data-security-center/user-guide/security-audit/","lastContentLink":"https://help.aliyun.com/zh/dsc/data-security-center/product-overview/difference-between-different-dsc-editions"}}]}],"card":[],"search":[],"infoCard":[{"bannerUrl":"https://img.alicdn.com/tfs/TB1Xf81a3gP7K4jSZFqXXamhVXa-5169-974.jpg","bannerTitle":"数据库审计","bannerContent":"满足等保2.0二级和三级 “安全审计”合规要求的同时，智能解析数据库通信流量，细粒度审计数据库访问行为，通过对数据库全量行为的审计溯源、危险攻击的实时告警、风险语句的智能预警，提供数据库资产最安全的监控保障。","liveButtonName":"查看详情","liveButtonLink":"https://www.aliyun.com/product/dbaudit?spm=5176.21213303.8115314850.1.faf453c9I9EKNe&scm=20140722.S_card@@%E5%8D%A1%E7%89%87@@1796._.ID_card@@%E5%8D%A1%E7%89%87@@1796-RL_%E6%95%B0%E6%8D%AE%E5%BA%93%E5%AE%A1%E8%AE%A1-OR_ser-V_2-P0_0","contentTitle":"满足等保2.0’安全审计‘的合规要求","homePageLink":"https://page.aliyun.com/form/act803688306/index.htm","homePageName":"7天试用","linkGroup":[{"linkContent":"发布包大小极致优化，节省流量和存储。"},{"linkContent":"服务迭代不再受发版限制，快速发布，快速迭代。"},{"linkContent":"业务开发效率更加优秀，一次开发，多端运行。"}]}],"title":{"mainTitle":"数据库审计","subtitle":"满足等保2.0二级和三级 “安全审计”合规要求的同时，智能解析数据库通信流量，细粒度审计数据库访问行为，通过对数据库全量行为的审计溯源、危险攻击的实时告警、风险语句的智能预警，提供数据库资产最安全的监控保障。","linkUrl":"https://www.aliyun.com/product/dbaudit?spm=5176.21213303.8115314850.1.faf453c9I9EKNe&scm=20140722.S_card@@%E5%8D%A1%E7%89%87@@1796._.ID_card@@%E5%8D%A1%E7%89%87@@1796-RL_%E6%95%B0%E6%8D%AE%E5%BA%93%E5%AE%A1%E8%AE%A1-OR_ser-V_2-P0_0","btnText":"查看详情"},"visual":{"topbg":"https://img.alicdn.com/tfs/TB1bQuBIYH1gK0jSZFwXXc7aXXa-3840-740.gif","icon":"","textColor":"dark"},"dataList":[{"summary":"啦啦啦","author":"wuwu","linksUrl":"#"}],"sceneCard":[],"txt":[]}}

数据库审计

满足等保2.0二级和三级 “安全审计”合规要求的同时，智能解析数据库通信流量，细粒度审计数据库访问行为，通过对数据库全量行为的审计溯源、危险攻击的实时告警、风险语句的智能预警，提供数据库资产最安全的监控保障。

产品控制台

立即购买

产品文档

精选推荐

包年享85折优惠

用户指南

产品快速入门

不同版本功能对比