zoukankan      html  css  js  c++  java
  • SQL OUTER JOIN

    When we want to select out all the record from two table, no matter it's present at second table or not, we will have to use SQL OUTER JOIN command.

    There are 3 type of OUTER JOIN, which is:
    LEFT OUTER JOIN
    RIGHT OUTER JOIN
    FULL OUTER JOIN

    SQL OUTER JOIN syntax:

    SELECT *
    FROM [TABLE 1] OUTER JOIN [TABLE 2]
    ON [TABLE 1].[COLUMN NAME 1] = [TABLE 2].[COLUMN NAME 2]


    EXAMPLE :

    Let's say we got 2 tables containt data like Below:

    Table 1: GameScores

    PlayerName DepartmentId Scores
    Jason 1 3000
    Irene 1 1500
    Jane 2 1000
    David 2 2500
    Paul 3 2000
    James 4 2000

    Table 2: Departments

    DepartmentId DepartmentName
    1 IT
    2 Marketing
    3 HR
    5 QA

    LEFT OUTER JOIN will return all records from the first table,
    SQL statement and Result for LEFT OUTER JOIN is :

    SELECT * FROM GameScores2
    LEFT OUTER JOIN Departments
    ON GameScores2.DepartmentId = Departments.DepartmentId

    Result:

    PlayerName DepartmentId Scores DepartmentId DepartmentName
    Jason 1 3000 1 IT
    Irene 1 3000 1 IT
    Jane 2 3000 2 Marketing
    David 2 3000 2 Marketing
    Paul 3 3000 3 HR
    James 4 2000 NULL NULL

    RIGHT OUTER JOIN will return all records from the second table,
    SQL statement and Result for RIGHT OUTER JOIN is :

    SELECT * FROM GameScores2
    RIGHT OUTER JOIN Departments
    ON GameScores2.DepartmentId = Departments.DepartmentId

    Result:

    PlayerName DepartmentId Scores DepartmentId DepartmentName
    Jason 1 3000 1 IT
    Irene 1 3000 1 IT
    Jane 2 3000 2 Marketing
    David 2 3000 2 Marketing
    Paul 3 3000 3 HR
    NULL NULL NULL 5 QA

    FULL OUTER JOIN will return all records from all tables,
    SQL statement and Result for FULL OUTER JOIN is :

    SELECT * FROM GameScores2
    FULL OUTER JOIN Departments
    ON GameScores2.DepartmentId = Departments.DepartmentId

    Result:

    PlayerName DepartmentId Scores DepartmentId DepartmentName
    Jason 1 3000 1 IT
    Irene 1 3000 1 IT
    Jane 2 3000 2 Marketing
    David 2 3000 2 Marketing
    Paul 3 3000 3 HR
    James 4 2000 NULL NULL
    NULL NULL NULL 5 QA
  • 相关阅读:
    OpenGL模板缓冲区与模板测试
    u3d调用c++ dll的DllNotFoundExceion 问题
    u3d调用自己的dll
    使用 idea 的Bookmarks(书签)功能
    maven 相关问题
    项目
    使用 vi/vim 时,粘贴进新创建文件或空文件的首行内容丢失的解决方法
    Thread.sleep还是TimeUnit.SECONDS.sleep
    搭建 Guacamole 并解决各种坑和创建不了虚拟驱动器导致无法实现文件传输的方法
    properJavaRDP 跑通本地远程桌面
  • 原文地址:https://www.cnblogs.com/zhoug2020/p/3327808.html
Copyright © 2011-2022 走看看