1

我有一个包含 2 列 Ex_Id 和 Term_Id 的表,它们都是 int 类型。我的表将有一个练习 ID 的多个术语 ID。

     Table would look like this:
      Ex_Id Term_Id
         1     2
         1     3
         1     4
         1     5
         2     2
         3     2
         3     4

等等。获取 Ex_Id 列表是首要要求。我的功能是这样的。

List<int> Get_ExId_List(List<int> lst_TermId)
{
    // return a list of Ex_Id <int>
}

也就是说,我将传递一个术语 ID 列表,并且我需要获取一个匹配某些条件的练习 ID 列表。这个伪代码可以更好地解释选择的标准:SELECT such Ex_Ids FROM table Exercise_Term WHERE Ex_Id has all the corresponding Term_Ids in the lst_TermId

例如,从我上面提供的示例表中,

List<int> Get_ExId_List([2])
{
    // return [1,2,3]
}

List<int> Get_ExId_List([2,4])
{
    // return [1,3]
}

List<int> Get_ExId_List([2,3,4])
{
    // return [1]
}

查询部分是我的困惑。在这种情况下查询会是什么样子?休息我能应付。希望问题很清楚。谢谢..

4

2 回答 2

2
SELECT Ex_ID 
FROM TableName 
WHERE Term_ID IN (?, ?, ?)                --- (2, 3, 4)
GROUP BY Ex_ID
HAVING COUNT(DISTINCT Term_ID) = 3        --- number of terms in the above list

如果该组合(Ex_ID, Term_ID)在表中是唯一的,则可以替换COUNT(DISTINCT Term_ID)COUNT(*)

这是一个关系划分问题。“标准”解决方案将使用两个否定(不存在):

SELECT DISTINCT Ex_ID
FROM TableName e
WHERE NOT EXISTS
        ( SELECT *
          FROM TableName t
          WHERE t.Term_ID IN (?, ?, ?)           --- the list of terms
            AND NOT EXISTS
                  ( SELECT *
                    FROM TableName a
                    WHERE a.Term_ID = t.Term_ID
                      AND a.Ex_ID = e.Ex_ID
                  )
        ) 

或者在你的情况下更好:

SELECT DISTINCT Ex_ID
FROM TableName e
WHERE NOT EXISTS
        ( SELECT *
          FROM
            ( SELECT ? AS Term_ID  
            UNION
              SELECT ?
            UNION 
              SELECT ?
            ) AS t
          WHERE NOT EXISTS
                  ( SELECT *
                    FROM TableName a
                    WHERE a.Term_ID = t.Term_ID
                      AND a.Ex_ID = e.Ex_ID
                  )
        ) 

于 2011-07-26T06:37:06.460 回答
1

您可以使用 LINQ。将整个表放入某种类型的 IEnumerable 中,然后使用 LINQ。这是一个例子:

static IEnumerable<int> Get_ExId_List(ICollection<int> lst_TermId)
{
    //this is just for the example - get the real data instead
    var data = new[] {
        new { Ex_Id = 1, Term_Id = 2},
        new { Ex_Id = 1, Term_Id = 3},
        new { Ex_Id = 1, Term_Id = 4},
        new { Ex_Id = 1, Term_Id = 5},
        new { Ex_Id = 2, Term_Id = 2},
        new { Ex_Id = 3, Term_Id = 2},
        new { Ex_Id = 3, Term_Id = 4},
    };

    return data
        .Where(row => lst_TermId.Contains(row.Term_Id))
        .GroupBy(row => row.Ex_Id)
        .Where(group => group.Count() == lst_TermId.Count())
        .Select(group => group.Key);
}

static void Main(string[] args)
{
    HashSet<int> lst_TermId = new HashSet<int>();
    lst_TermId.Add(2);

    Console.WriteLine();
    var result = Get_ExId_List(lst_TermId);
    foreach (var exid in result)
        Console.WriteLine(exid);

    lst_TermId.Add(4);

    Console.WriteLine();
    result = Get_ExId_List(lst_TermId);
    foreach (var exid in result)
        Console.WriteLine(exid);

    lst_TermId.Add(3);

    Console.WriteLine();
    result = Get_ExId_List(lst_TermId);
    foreach (var exid in result)
        Console.WriteLine(exid);
}

请注意,如果您的 lst_TermId 是 a ,您将获得更好的性能HashSet<int>,因为 contains 方法将O(1)代替O(n).

于 2011-07-26T06:50:23.783 回答