linq语句两表左联(多条件联合) 无数据赋值 || A表多次左联B表(含根据条件拼接linq)

最新推荐文章于 2025-05-27 08:00:00 发布

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最新推荐文章于 2025-05-27 08:00:00 发布

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分类专栏：数据库查询语句

本文链接：https://blog.youkuaiyun.com/niuniuyaobuyao/article/details/80422300

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这篇博客介绍了如何使用LINQ进行两表的左连接查询，特别是在没有匹配数据时的处理策略。同时，文章探讨了在A表中通过多个编码字段与B表进行多次联接的情况，包括根据条件动态拼接LINQ查询的方法。

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linq语句两表左联(多条件联合) 无数据赋值

var Editquery=from table in query
                              join dyTable in dyTableQuery 
                              on new {TableMC= table.MC,tableTypeName=table.TABLE_NAME }  equals new { TableMC = dyTable.BMMC, tableTypeName = dyTable.BM_TABLENAME }
                              into newQuery
                              from A in newQuery.DefaultIfEmpty()
                              select new Model.CorrespondingTableInfo
                              {
                                  BM= table.BM,
                                  MC = table.MC,
                                  TABLE_NAME=table.TABLE_NAME,
                                  IsHaveDY = A != null ? true : false
                              };


                return Editquery.ToList();

--------------------A表多次左联B表(含根据条件拼接linq)，因为A表里有3个列存编码要去B表查名称-------------------------------------------

var query = from s in Employees
                        join departpent in Departments on s.FunctionDepartment equals departpent.Code into FunctionName
                        from FName in FunctionName.DefaultIfEmpty()
                        join departpent2 in Departments on s.OutpatientDepartment equals departpent2.Code into OutName
                        from OName in OutName.DefaultIfEmpty()
                        join departpent3 in Departments on s.InpatientDepartment equals departpent3.Code into InName
                        from IName in InName.DefaultIfEmpty()
                        select new Model.EmployeeInfo
                        {
                            OutpatientDepartment = s.OutpatientDepartment.TrimEnd(),
                            InpatientDepartment = s.InpatientDepartment.TrimEnd(),
                            FunctionDepartment = s.FunctionDepartment.TrimEnd(),
                            FunctionDepartmentName = FName.Name ?? "",
                            OutpatientDepartmentName = OName.Name ?? "",
                            InpatientDepartmentName = IName.Name ?? "",
                            EmpNo = s.EmpNo.TrimEnd(),
                            Name = s.Name.TrimEnd(),
                        };
            if (!string.IsNullOrEmpty(EmpNoOrName))
            {
                query = query.Where(s => s.EmpNo.Contains(EmpNoOrName) || s.Name.Contains(EmpNoOrName));
            }
            else if (!string.IsNullOrEmpty(strDepartmentCode))
            {
                query = query.Where(s=>s.InpatientDepartment== strDepartmentCode||s.FunctionDepartment== strDepartmentCode||s.OutpatientDepartment== strDepartmentCode);
            }
            return query.ToList();