我正在编写一个查询
SELECT * FROM EMPLOYEES WHERE EMP_ID IN (10,5,3,9,2,8,6)
Emp_id Emp_Name
10 John
5 Joe
3 Tippu
9 Rich
2 Chad
8 Chris
6 Rose
基本上和IN Clause的顺序一样。这个可行吗？请告诉我。
PS: 我可以在SQL中完成，或者在获得结果集后，如果我可以使用LINQ或其他东西在前端选项中进行排序也可以（我在前端有Emp IDs数组）
谢谢
字符串评论答案；这将产生与原始答案相同的结果，但匹配字符串：
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;
});
顺便说一句，原始答案加上以下两行可能会更好：
string orgList = "10,5,3,9,2,8,6";
List<int> orderArray = new List<int>(orgList.Split(",".ToCharArray()));
使用整数常量的替代方法。使用上面的代码将按照任意逗号分隔的整数列表进行排序。
Linq 中以下的解决方案给出了这个结果：
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; }
}
糟糕的 SQL 原始答案
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
什么？Linq-To-SQL没有一个神奇的按钮可以按下让它完成这个功能吗？ :-)
要在SQL Server中完成此操作，您需要一个函数将列表转换为集合并且保持顺序。有许多方法可以解决这个问题，这里是其中之一：
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
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];
一个更好的方法是完全停止传递逗号分隔列表，而是使用表值参数。这是一组事物，而不是字符串或某些 JSON 词汇。在 C# 代码中创建一个 DataTable，其中包含两列，列表和顺序。然后创建一个表类型：
CREATE TYPE dbo.SortedList AS TABLE(ID INT, [Order] INT);
然后是一个以此参数为输入的存储过程：
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