当前位置:网站首页>SQL第二章第三章
SQL第二章第三章
2020-11-09 10:51:00 【osc_ptcuqdug】
1:插入数据
或者
2:显示数据
SELECT * FROM 表名
3:数据更新
4:WHERE子句
比较运算符,确定
1:查询
SELECT语句
2:唯一值、
SELECT DISTINCT 列名 FROM 表名;
3:WHERE 子句过滤结果
解释上面代码意思
4:逻辑运算符号
表中的运算级顺序是从高到底的
1:AND OR
WHERE子句后面的运算条件按照AND>OR的顺序
2:not运算符号
NOT和<>是同一个意思,都是不等于的意思。不为真。
3:BETWEEN运算符
BETWEEN 指定了一个范围,其中这个范围在一个值到另一个值之间。
4:LIKE运算符
LIKE运算符后面可以跟通配符
5:IN运算符号
5:ORDER BY 排序
正序排序
倒序排序
特别注意,就算是不显示表里面的某一行,也可以用这一行进行进行排序。
6:在多个表中选择数据
要注意那一列,展示了表的联合。
7:NULL数据
NULL表示未知,并不等同于没有。
版权声明
本文为[osc_ptcuqdug]所创,转载请带上原文链接,感谢
https://my.oschina.net/u/4308645/blog/4708846
边栏推荐
- Have you ever thought about why the transaction and refund have to be split into different tables
- 操作系统之bios
- B. protocal has 7000eth assets in one week!
- 深度优先搜索和广度优先搜索
- 日志分析工具 - GoAccess
- After Android solves the setrequested orientation, the rotation of the mobile phone screen does not trigger the onconfigurationchanged method
- 常见特征金字塔网络FPN及变体
- Commodity management system -- integrate warehouse services and obtain warehouse list
- When Python calls ffmpeg, 'ffmpeg' is not an internal or external command, nor a runnable program
- 5 个我不可或缺的开源工具
猜你喜欢
1.操作系统是干什么的?
【QT】子类化QThread实现多线程
1486. Array XOR operation
How does semaphore, a thread synchronization tool that uses an up counter, look like?
Huawei HCIA notes
Depth first search and breadth first search
GDI 及OPENGL的区别
A few lines of code can easily transfer traceid across systems, so you don't have to worry about losing the log!
Talk about my understanding of FAAS with Alibaba cloud FC
ubuntu 上使用微信的新方案——手机投屏
随机推荐
Android 解决setRequestedOrientation之后手机屏幕的旋转不触发onConfigurationChanged方法
ThinkPHP框架执行流程源码解析
为什么我们不使用GraphQL? - Wundergraph
首次开通csdn,这篇文章送给过去的自己和正在发生的你
How does semaphore, a thread synchronization tool that uses an up counter, look like?
LTM understanding and configuration notes
Do you know how the computer starts?
A brief introduction of C code to open or close the firewall example
The vowels in the inverted string of leetcode
20201108编程练习——练习3
Chrome浏览器引擎 Blink & V8
Android emulator error: x86 emulation currently requires hardware acceleration solution
This program cannot be started because msvcp120.dll is missing from your computer. Try to install the program to fix the problem
Chapter 5 programming
C + + adjacency matrix
5 个我不可或缺的开源工具
LTM理解及配置笔记记录
The whole process of building a fully distributed cluster
向北京集结!OpenI/O 2020启智开发者大会进入倒计时
开源 | HMGNN:异构小图神经网络及其在拉新裂变风控场景的应用