今天学习了一下Oracle中窗口函数的使用,所以将自己的学习心得分享给大家。有时候查询,我们需要将我们的结果显示在每条记录里,
今天学习了一下Oracle中窗口函数的使用,所以将自己的学习心得分享给大家。
使用窗口函数可以解决一些问题。比如说如果我们有两张表,一张教师的表,一张系的表,如果我们想查询每个系的老师的平均工资,这当然没什么问题,但是如果加上同时把老师的信息查询出来,那么就麻烦了,我们需要将每个系的老师的平均工资看成一张临时表,来和原先的老师的表进行连接查询;或者说查询每个系工资最高的老师的信息,有些的时候,像这种分组的,多表的,统计的,经常涉及查询每个查询的具体信息,写的时候增加了我们的难度,如果使用窗口函数,再配合一些其他的函数使用,很简单的就可以解决这个问题。
有时候查询,我们需要将我们的结果显示在每条记录里,Oracle中的这个窗口函数就可以解决这个问题。
窗口函数的名字是over()函数,常用的有两个属性partition by和order by,partition by类似于group by,我们通常将group by叫做分组,而partition by称作分区,分组返回通常是一行,partition by返回的是多行。
如果将Oracle中的这个over()函数和其他的函数联合使用将会发挥更大的作用,比如最值的问题,获取其他行的数据等。
相关阅读:Oracle窗口函数基础知识学习
1、和统计函数(聚合函数)使用
可以和count() 、sum() 、avg() 、min() 、max()这些函数使用,这样在查询市,还可以显示每条记录的信息,比如说查询每个系的老师的平均工资和老师的信息,,如图所示:
2、和排名函数使用
有时在后台查询数据库时,需要向前台那样显示序号,oracle提供了三个函数,搭配over()函数更有用。如图所示:
3、和错行的函数使用
Oracle中有两个类似于错行的行数,在本行可以取到其他行的数据。lead 函数和lag函数。如图所示:
4、取最值的函数first_value()
通过和该函数的联合使用,可以解决最值问题。常用的有两外的属性值。
无论是那种方式都会在查询的记录上添加一列的信息,有时候需要这种需求,使用这个函数还可以解决使用group by时,只能查询分组的字段值的问题。

This article explores optimizing MySQL memory usage in Docker. It discusses monitoring techniques (Docker stats, Performance Schema, external tools) and configuration strategies. These include Docker memory limits, swapping, and cgroups, alongside

This article addresses MySQL's "unable to open shared library" error. The issue stems from MySQL's inability to locate necessary shared libraries (.so/.dll files). Solutions involve verifying library installation via the system's package m

The article discusses using MySQL's ALTER TABLE statement to modify tables, including adding/dropping columns, renaming tables/columns, and changing column data types.

This article compares installing MySQL on Linux directly versus using Podman containers, with/without phpMyAdmin. It details installation steps for each method, emphasizing Podman's advantages in isolation, portability, and reproducibility, but also

This article provides a comprehensive overview of SQLite, a self-contained, serverless relational database. It details SQLite's advantages (simplicity, portability, ease of use) and disadvantages (concurrency limitations, scalability challenges). C

This guide demonstrates installing and managing multiple MySQL versions on macOS using Homebrew. It emphasizes using Homebrew to isolate installations, preventing conflicts. The article details installation, starting/stopping services, and best pra

Article discusses configuring SSL/TLS encryption for MySQL, including certificate generation and verification. Main issue is using self-signed certificates' security implications.[Character count: 159]

Article discusses popular MySQL GUI tools like MySQL Workbench and phpMyAdmin, comparing their features and suitability for beginners and advanced users.[159 characters]


Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

AI Hentai Generator
Generate AI Hentai for free.

Hot Article

Hot Tools

SublimeText3 Chinese version
Chinese version, very easy to use

SublimeText3 Mac version
God-level code editing software (SublimeText3)

MantisBT
Mantis is an easy-to-deploy web-based defect tracking tool designed to aid in product defect tracking. It requires PHP, MySQL and a web server. Check out our demo and hosting services.

Dreamweaver CS6
Visual web development tools

DVWA
Damn Vulnerable Web App (DVWA) is a PHP/MySQL web application that is very vulnerable. Its main goals are to be an aid for security professionals to test their skills and tools in a legal environment, to help web developers better understand the process of securing web applications, and to help teachers/students teach/learn in a classroom environment Web application security. The goal of DVWA is to practice some of the most common web vulnerabilities through a simple and straightforward interface, with varying degrees of difficulty. Please note that this software
