按IN的順序對SQL查詢進行排序

Question

我正在寫一個查詢

SELECT * FROM EMPLOYEES WHERE EMP_ID IN (10,5,3,9,2,8,6)

我希望結果應按以下順序排列

Emp_id   Emp_Name
10       John
5        Joe
3        Tippu
9        Rich
2        Chad
8        Chris
6        Rose

基本上與IN子句的順序相同。 有可能嗎？ 請告訴我。

PS：我可以在SQL中執行此操作，也可以在獲取結果集后如果我可以使用LINQ或者在前端選項中進行排序選項也適用於我（我在前端有數組中的Emp ID）

謝謝

Answer 1

字符串評論答案; 這將給出與原始答案相同但在字符串上匹配的結果：

  string orgList = "John,Joe,Tippu,Rich,Chad,Chris,Rose";
  List<string> orderArray = new List<string>(orgList.Split(",".ToCharArray()));

  // the linq to do the ordering
  var result = ourList.OrderBy(e => {
     int loc = orderArray.IndexOf(e.Name);
     return loc == -1? int.MaxValue: loc;
  });

作為旁注，這兩行可能會更好：

  string orgList = "10,5,3,9,2,8,6";
  List<int> orderArray = new List<int>(orgList.Split(",".ToCharArray()));

而不是使用整數常量。 使用上面的代碼將按任意逗號分隔的整數列表排序。

Linq中的解決方案給出了以下結果：

void Main()
{
  // some test data
  List<Person> ourList = new List<Person>() 
  {
    new Person() { ID = 1, Name = "Arron" },
    new Person() { ID = 2, Name = "Chad" },
    new Person() { ID = 3, Name = "Tippu" },
    new Person() { ID = 4, Name = "Hogan" },
    new Person() { ID = 5, Name = "Joe" },
    new Person() { ID = 6, Name = "Rose" },
    new Person() { ID = 7, Name = "Bernard" },
    new Person() { ID = 8, Name = "Chris" },
    new Person() { ID = 9, Name = "Rich" },
    new Person() { ID = 10, Name = "John" }
  };

  // what we will use to order
  List<int> orderArray = new List<int>(){10,5,3,9,2,8,6};

  // the linq to do the ordering
  var result = ourList.OrderBy(e => {
     int loc = orderArray.IndexOf(e.ID);
     return loc == -1? int.MaxValue: loc;
  });

  // good way to test using linqpad (get it at linqpad.com
  result.Dump();
}

// test class so we have some thing to order
public class Person
{
   public int ID { get; set; }
   public string Name { get; set; }
}

---

原來不好的SQL答案

WITH makeMyOrder
(
   SELECT 10 as ID, 1 as Ord
     UNION ALL
   SELECT 5 as ID, 2 as Ord
     UNION ALL
   SELECT 3 as ID, 3 as Ord
     UNION ALL
   SELECT 9 as ID, 4 as Ord
     UNION ALL
   SELECT 2 as ID, 5 as Ord
     UNION ALL
   SELECT 8 as ID, 6 as Ord
     UNION ALL
   SELECT 6 as ID, 7 as Ord
),
SELECT * 
FROM EMPLOYEES E
JOIN makeMyOrder O ON E.EMP_ID = O.ID
ORDER BY O.Ord

Answer 2

什么，Linq-To-SQL沒有魔術按鈕你可以按它來做到這一點？ :-)

要在SQL Server中執行此操作，您需要一個將列表轉換為集合並維護訂單的函數。 這種貓的皮膚有很多種方法; 這是一個：

CREATE FUNCTION dbo.SplitInts_Ordered
(
    @List       VARCHAR(MAX),
    @Delimiter  VARCHAR(255)
)
RETURNS TABLE
AS
    RETURN (SELECT [Index] = ROW_NUMBER() OVER (ORDER BY Number), Item 
    FROM (SELECT Number, Item = CONVERT(INT, SUBSTRING(@List, Number, 
        CHARINDEX(@Delimiter, @List + @Delimiter, Number) - Number))
      FROM (SELECT ROW_NUMBER() OVER (ORDER BY [object_id])
        FROM sys.all_objects) AS n(Number)
    WHERE Number <= CONVERT(INT, LEN(@List))
      AND SUBSTRING(@Delimiter + @List, Number, LEN(@Delimiter)) = @Delimiter
    ) AS y);
GO

現在你可以說：

DECLARE @list VARCHAR(MAX);

SET @list = '10,5,3,9,2,8,6';

SELECT e.Emp_Id, e.Emp_Name -- never use * in production code
  FROM dbo.Employees AS e -- always use schema prefix
  INNER JOIN dbo.SplitInts_Ordered(@list, ',') AS x
  ON x.Item = e.Emp_Id
  ORDER BY x.[Index];

一個更多，更多，更好，更好的方法是停止傳遞逗號分隔列表，並使用表值參數。 這是一組東西，不是字符串或一些JSON淫穢。 在C＃代碼中創建一個DataTable，包含兩列，列表和順序。 然后創建一個表類型：

CREATE TYPE dbo.SortedList AS TABLE(ID INT, [Order] INT);

然后是一個以此為參數的存儲過程：

CREATE PROCEDURE dbo.GetTheList
  @x dbo.SortedList READONLY
AS
BEGIN
  SET NOCOUNT ON;

  SELECT e.Emp_Id, e.Emp_Name
    FROM dbo.Employees AS e
    INNER JOIN @x AS x
    ON x.ID = e.Emp_Id
    ORDER BY x.[Order];
END
GO

你是否可以用Linq-To-SQL做到這一點，我不確定; 人們似乎很快就跳上了Linq的潮流，因為它讓事情變得如此簡單。 好吧，只要你不需要實際做任何事情。