IDEA2023.1.3破解,IDEA破解,IDEA 2023.1破解,最新IDEA激活码

四十五、5.9 表关联操作

IDEA2023.1.3破解,IDEA破解,IDEA 2023.1破解,最新IDEA激活码

文章永久连接:https://tech.souyunku.com/?p=8310

JFinal ActiveRecord 天然支持表关联操作,并不需要学习新的东西,此为无招胜有招。表 关联操作主要有两种方式:一是直接使用 sql 得到关联数据;二是在 Model 中添加获取关联数据的方法。

假定现有两张数据库表:user、blog,并且 user 到 blog 是一对多关系,blog 表中使用 user_id关联到 user 表。如下代码演示使用第一种方式得到 user_name:

public void relation() {
String sql = “select b.*, u.user_name from blog b inner join user u on b.user_id=u.id where b.id=?”;
Blog blog = Blog. dao.findFirst(sql, 123); String name = blog.getStr(“user_name”);
}

以下代码演示第二种方式在 Blog 中获取相关联的 User 以及在 User 中获取相关联的Blog:

public class Blog extends Model{
public static final Blog dao = new Blog();

public User getUser() {
return User. dao.findById(get(“user_id”));
}
}
public class User extends Model{
public static final User dao = new User();

public List getBlogs() {
return Blog. dao.find(“select * from blog where user_id=?”, get(“id”));
}
}

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未经允许不得转载:搜云库技术团队 » 四十五、5.9 表关联操作

IDEA2023.1.3破解,IDEA破解,IDEA 2023.1破解,最新IDEA激活码
IDEA2023.1.3破解,IDEA破解,IDEA 2023.1破解,最新IDEA激活码

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