如何将列表添加到 SQL 数据库(使用 java) [英] How to add a list to a SQL database (using java)
问题描述
我是 sql 的新手,我想知道如何将列表添加到数据库中.这是我的意思:
I am new to sql and I was wondering how i can add a list to a database. Here is what I mean:
我有一个这样的java类,我想将其信息插入到数据库中:
I have an a java class like this that i want to insert its info into a db:
public class Dog{
private int dog_id;
private String dog_name;
private ArrayList<String> dog_friends;
}
每个狗对象都有不同数量的朋友.我的问题是如何将此列表添加到数据库中.我计划有 3 列(id、name、list),我只是不知道如何添加列表.
Every dog object will have a different amount size of friends. My question is how i can add this list to the db. I was planning on having 3 columns (id,name,list), I just dont know how to add a list.
推荐答案
你所拥有的是,在关系数据库世界中,称为一对多关系,它需要两个数据库表来表示信息.
What you have is, in the relational database world, called a one-to-many relationship, and it requires two database tables to represent the information.
在您的第一个表中,您将拥有 id
和 name
;在您的第二个表中,您将拥有 dog_id
、friend_id
和 dog_friend
.
In your first table, you'll have id
and name
; in your second table you'll have dog_id
, friend_id
and dog_friend
.
对于第一个表中的每个条目,第二个表中可能有很多条目.当您在第二个表中插入一行时,请确保将 dog_id
设置为与第一个表中的 id
匹配.
There will be possibly many entries in the second table for every entry in the first table. When you insert a row in the second table, be sure to set dog_id
to match the id
in the first table.
通过这种结构,您可以在 SQL 查询中使用 JOIN
来一次性获取所有信息,也可以根据需要独立查询表.
With this structure, you can use JOIN
s in your SQL query to get all the information at once, or query the tables independently, depending on your needs.
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