zoukankan      html  css  js  c++  java
  • 结合两张表person和address

    Table: Person

    +-------------+---------+
    | Column Name | Type    |
    +-------------+---------+
    | PersonId    | int     |
    | FirstName   | varchar |
    | LastName    | varchar |
    +-------------+---------+
    PersonId is the primary key column for this table.
    

    Table: Address

    +-------------+---------+
    | Column Name | Type    |
    +-------------+---------+
    | AddressId   | int     |
    | PersonId    | int     |
    | City        | varchar |
    | State       | varchar |
    +-------------+---------+
    AddressId is the primary key column for this table.



    为报表编写一个SQL查询,为Person表中的每个人提供以下信息,而不管这些人是否有地址:
    FirstName ,LastName,City ,State


    根据条件不管这些人是否有地址,如果用inner join 那么在地址表中,没用地址的人们将不会出现结果中。所以用左外连接。
    select p.FirstName,p.lastname,a.city,a.state from person p left join address a on p.personId = a.personId
    因为查询字段在两张表中是唯一的,所以可以省略表前缀,写成
    select FirstName ,LastName ,city ,state from person left join address on Person.personId = address.personId
  • 相关阅读:
    UPC2018组队训练赛第十二场
    ACM-ICPC 2018南京赛区网络预选赛
    UPC2018组队训练赛第十一场
    UPC2018组队训练赛第十场
    UPC2018组队训练赛第九场
    linux 用简单密码
    设置分辨率
    packstack
    rbenv
    elasticsearch
  • 原文地址:https://www.cnblogs.com/jiangshengxiang/p/8420776.html
Copyright © 2011-2022 走看看