LINQ的左连接、右连接、内连接

SQL连接类型详解

最新推荐文章于 2025-04-19 17:51:13 发布

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最新推荐文章于 2025-04-19 17:51:13 发布

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原文链接：http://www.cnblogs.com/zhangwc/p/8944725.html

本文详细介绍了SQL中的三种连接类型：左连接、右连接和内连接。通过具体的代码示例展示了如何使用这些连接来操作数据库表，帮助读者更好地理解并掌握不同连接方式的应用场景。

1、左连接：

var LeftJoin = from emp in ListOfEmployees
join dept in ListOfDepartment
on emp.DeptID equals dept.ID into JoinedEmpDept
from dept in JoinedEmpDept.DefaultIfEmpty()
select new
{
EmployeeName = emp.Name,
DepartmentName = dept != null ? dept.Name : null
};

2、右连接：

var RightJoin = from dept in ListOfDepartment
join employee in ListOfEmployees
on dept.ID equals employee.DeptID into joinDeptEmp
from employee in joinDeptEmp.DefaultIfEmpty()
select new
{
EmployeeName = employee != null ? employee.Name : null,
DepartmentName = dept.Name
};

3、内连接：

var query = from t in entitiy.TB_GCGL_ADA_USER
join p in entitiy.TB_GCGL_ZY_ZYK
on t.ETPRS_CODE equals p.ETPRS_CODE

                 select new TB_USER_ZYK
                 {
                    USER_ID = t.USER_ID,
                    USER_NAME = t.USER_NAME,
                    USER_PASSWORD = t.USER_PASSWORD,

};

转载于:https://www.cnblogs.com/zhangwc/p/8944725.html