從查詢 postgresql 轉換為 linq C#

Question

我想使用帶有“string_agg”的“groupby”與 linq 一起工作，但我無法從此查詢中找到參考。

SELECT DISTINCT "TB_M_GROUP_EMP"."GROUP_ID" AS "ID", 
  string_agg(Distinct "TB_M_EMPLOYEES"."EMP_NAME",',' order by "TB_M_EMPLOYEES"."EMP_NAME" ) as "Employee Name"
FROM public."TB_M_GROUP_EMP", "TB_M_EMPLOYEES"
GROUP BY "TB_M_GROUP_EMP"."GROUP_ID";

或此代碼

SELECT DISTINCT "TB_M_GROUP_EMP"."GROUP_ID" as "Group Id", array_agg(Distinct"TB_M_EMPLOYEES"."EMP_CODE" || ',' ||"TB_M_EMPLOYEES"."EMP_NAME"|| ',' ||"TB_M_EMPLOYEES"."EMP_EMAIL" ) as "Employees"
FROM public."TB_M_GROUP_EMP", "TB_M_EMPLOYEES"
GROUP BY "TB_M_GROUP_EMP"."GROUP_ID";

請幫助將此查詢轉換為 linq C# 並提供參考或文檔 linq！

我曾嘗試使用此代碼，但這並不是我想要的輸出。

groupEmployee
   .GroupBy(e => new { e.GroupId, e.Employee }, (key, group) => new
   {
      Employee = key.Employee,
      Employees = group.ToList()
   })

示例表：

--------------
TB_M_EMPLOYEES
--------------
|EMP_ID|EMP_CODE|EMP_NAME|EMP_EMAIL|
------------------------------------
|1     |E0012   |Ali     |@ali     |
|2     |E0013   |AL      |@al      |
|3     |E0014   |Abi     |@abi     |
|4     |E0015   |Ad      |@ad      |
|5     |E0016   |Ea      |@ea      |

----------------------
TB_M_GROUP_EMP
----------------------
|Id|GROUP_ID|EMP_ID|
----------------------
|1 |1       |1     |
|2 |1       |2     |
|3 |1       |3     |
|4 |1       |4     |
|5 |1       |5     |

從上面的兩個表。 我希望輸出是這個底部的表格。

TB_M_GROUP_EMP
-----------------
|GROUP_ID|EMP|
-----------------
|1       |{"E0012,Ali,@ali","E0013,Al,@al","E0014,Abi,@abi","E0015,Ad,@ad","E0016,Ea,@ea"}|

謝謝。

Answer 1

查看：

https://docs.microsoft.com/en-us/dotnet/api/system.linq.enumerable.aggregate?view=netcore-3.1

前任。

items.Aggregate((i, j) => i + delimiter + j));

這可能不會產生相同的 SQL 語句 - 因此您可能必須優化性能。

Answer 2

也許您可以使用 LINQ 鍵入：

var result =
        from employee in groupEmployee
        group employee by employee.GroupId into output
        select output;

現在你有你的輸出結果。 為了回答您的問題，我使用了以下文章： https : //docs.microsoft.com/en-gb/dotnet/csharp/linq/group-query-results

Answer 3

假設我們有以下模型：

public class Employee
{
    public int EmployeeId { get; set; }
    public string Code { get; set; }
    public string Name { get; set; }
    public string Email { get; set; }
}

public class EmployeeGroup
{
    public int Id { get; set; }
    public int GroupId { get; set; }
    public int EmployeeId { get; set; }
}

試試看，如下：

var result = groups
    .Join(employees, grp => grp.EmployeeId, emp => emp.EmployeeId, (group, employee) => 
        new
        {
            group.GroupId,
            employee.EmployeeId,
            employee.Code,
            employee.Name,
            employee.Email,
        })
    .GroupBy(res => res.GroupId)
    .Select(res => new
    {
        GroupId = res.Key,
        Names = string.Join(",", res
                        .OrderBy(e => e.Name)
                        .Select(e => $"{e.Code},{e.Name},{e.Email}"))
    })
    .ToList();

然而，這里的另一個版本可能是（可能更接近您想要的輸出）：

var result = groups.GroupJoin(employees, grp => grp.EmployeeId, emp => emp.EmployeeId,
    (grp, emp) => new
    {
        grp.GroupId,
        Names = string.Join(",", emp.Select(e => $"{e.Code},{e.Name},{e.Email}"))
    }).
    GroupBy(e=> e.GroupId)
    .ToList();

如果您想要上面的有序（按名稱）版本，那么查詢可能會變得更復雜一些：

var result = groups
    .GroupJoin(employees,
        grp => grp.EmployeeId,
        emp => emp.EmployeeId,
        (grp, emps) =>
        {
            var empsList = emps.ToList();

            return new
            {
                grp.GroupId,
                NamesCmp = empsList.Select(e => e.Name).FirstOrDefault(), // this needed for Ordering
                Names = string.Join(",", empsList.Select(e => $"{e.Code},{e.Name},{e.Email}"))
            };
        })
    .GroupBy(e => e.GroupId)
    .Select(grp => new
    {
        GroupId = grp.Key,
        Items = grp.OrderBy(g => g.NamesCmp)
            .Select(g => g.Names)
    })
    .ToList();

---

請注意，對上述使用真實類模型而不是匿名類型更可取。

Answer 4

根據我的理解，您正在尋找以下解決方案。 如果我錯過了什么，請告訴我。

1. 首先根據 EMP_ID 連接兩個表
2. 按 GROUP_ID 列分組。
3. 使用 string.Join 連接 $""{e.EMP_CODE},{e.EMP_NAME},{e.EMP_EMAIL}""。

下面是代碼：

var result = (from empRow in TB_M_EMPLOYEES.AsEnumerable()
                      join grpRow in TB_M_GROUP_EMP.AsEnumerable()
                      on empRow.Field<string>("EMP_ID") equals grpRow.Field<string>("EMP_ID")
                      select new
                      {
                          EMP_ID = empRow.Field<string>("EMP_ID"),
                          EMP_CODE = empRow.Field<string>("EMP_CODE"),
                          EMP_NAME = empRow.Field<string>("EMP_NAME"),
                          EMP_EMAIL = empRow.Field<string>("EMP_EMAIL"),
                          GROUP_ID = grpRow.Field<string>("GROUP_ID")
                      }).GroupBy(r => r.GROUP_ID)
                        .Select(rs => new
                        {
                            GroupId = rs.Key,
                            FinalNames = string.Join(",", rs
                                            .Select(e => $"\"{e.EMP_CODE},{e.EMP_NAME},{e.EMP_EMAIL}\""))
                        });

測試功能如下：

static void PostResSql()
    {
        DataTable TB_M_EMPLOYEES = new DataTable();

        TB_M_EMPLOYEES.Columns.Add("EMP_ID");
        TB_M_EMPLOYEES.Columns.Add("EMP_CODE");
        TB_M_EMPLOYEES.Columns.Add("EMP_NAME");
        TB_M_EMPLOYEES.Columns.Add("EMP_EMAIL");

        DataTable TB_M_GROUP_EMP = new DataTable();
        TB_M_GROUP_EMP.Columns.Add("Id");
        TB_M_GROUP_EMP.Columns.Add("GROUP_ID");
        TB_M_GROUP_EMP.Columns.Add("EMP_ID");

        DataRow row = TB_M_EMPLOYEES.NewRow();
        row[0] = "1";
        row[1] = "E0012";
        row[2] = "Ali";
        row[3] = "@ali";
        TB_M_EMPLOYEES.Rows.Add(row);

        row = TB_M_EMPLOYEES.NewRow();
        row[0] = "2";
        row[1] = "E0013";
        row[2] = "AL";
        row[3] = "@al";
        TB_M_EMPLOYEES.Rows.Add(row);

        row = TB_M_EMPLOYEES.NewRow();
        row[0] = "3";
        row[1] = "E0014";
        row[2] = "Abi";
        row[3] = "@abi";
        TB_M_EMPLOYEES.Rows.Add(row);

        row = TB_M_EMPLOYEES.NewRow();
        row[0] = "4";
        row[1] = "E0015";
        row[2] = "Ad";
        row[3] = "@ad";
        TB_M_EMPLOYEES.Rows.Add(row);

        row = TB_M_EMPLOYEES.NewRow();
        row[0] = "5";
        row[1] = "E0016";
        row[2] = "Ea";
        row[3] = "@ea";
        TB_M_EMPLOYEES.Rows.Add(row);


        row = TB_M_GROUP_EMP.NewRow();
        row[0] = "1";
        row[1] = "1";
        row[2] = "1";
        TB_M_GROUP_EMP.Rows.Add(row);

        row = TB_M_GROUP_EMP.NewRow();
        row[0] = "2";
        row[1] = "1";
        row[2] = "2";
        TB_M_GROUP_EMP.Rows.Add(row);

        row = TB_M_GROUP_EMP.NewRow();
        row[0] = "3";
        row[1] = "1";
        row[2] = "3";
        TB_M_GROUP_EMP.Rows.Add(row);

        row = TB_M_GROUP_EMP.NewRow();
        row[0] = "4";
        row[1] = "1";
        row[2] = "4";
        TB_M_GROUP_EMP.Rows.Add(row);

        row = TB_M_GROUP_EMP.NewRow();
        row[0] = "5";
        row[1] = "1";
        row[2] = "5";
        TB_M_GROUP_EMP.Rows.Add(row);


        var result = (from empRow in TB_M_EMPLOYEES.AsEnumerable()
                      join grpRow in TB_M_GROUP_EMP.AsEnumerable()
                      on empRow.Field<string>("EMP_ID") equals grpRow.Field<string>("EMP_ID")
                      select new
                      {
                          EMP_ID = empRow.Field<string>("EMP_ID"),
                          EMP_CODE = empRow.Field<string>("EMP_CODE"),
                          EMP_NAME = empRow.Field<string>("EMP_NAME"),
                          EMP_EMAIL = empRow.Field<string>("EMP_EMAIL"),
                          GROUP_ID = grpRow.Field<string>("GROUP_ID")
                      }).GroupBy(r => r.GROUP_ID)
                        .Select(rs => new
                        {
                            GroupId = rs.Key,
                            FinalNames = string.Join(",", rs
                                            .Select(e => $"\"{e.EMP_CODE},{e.EMP_NAME},{e.EMP_EMAIL}\""))
                        });
    }