Question

同一服务器（SQL Server）中有多个数据库。我的要求是当在C＃Windows窗体应用程序中给出GUID输入时，我必须在所有数据库中查询与该GUID相对应的详细信息并在应用程序中显示它。表名在所有数据库中都相同。也就是说，如果在一个数据库中找不到详细信息，那么我必须检入另一个数据库（在同一服务器内）并且必须遍历循环。但是，由于有超过10个数据库，因此会达到性能。那么，有没有办法以有效的方式获取细节？我已经广泛搜索但找不到任何解决方案

我没有权限在数据库服务器中创建类似View的权限。我有权仅使用选择查询从任何这些数据库中获取数据

如果需要更多细节，请告诉我

Answer 1

根据您提供的信息，听起来您需要查看许多数据库，但是您只需要遍历它们，直到找到所需内容，或直到您用完数据库进行查看。这意味着如果您在DB＃3中找到所需内容，则不应进入DB＃4，＃5，依此类推。希望这会有所帮助。对于我来说，这个伟大的表示你不需要查询你不需要的DB。

    public Form1()
    {
        InitializeComponent();
        string textThatWouldBeInATextBoxOnTheUserInterface = "1234,4567,789";//lets pretend this is the textbox value entered by the user
        string[] GUIDs = textThatWouldBeInATextBoxOnTheUserInterface.Split(',').ToArray();//split that string into a string[]
        List<string> listOfResults = new List<string>();//create something to hold your results

        //iterate through each string
        foreach (string item in GUIDs)
        {
            listOfResults.Add(getTheData(item));//add results to your list
        }
    }

    private string getTheData(string incomingID)
    {
        List<string> dbConnStrings = new List<string>();
        dbConnStrings.Add(@"Provider=SQLOLEDB;Server=ServerName\Schema;Database=dbName1;User Id=uid;Password=pwd;");
        dbConnStrings.Add(@"Provider=SQLOLEDB;Server=ServerName\Schema;Database=dbName2;User Id=uid;Password=pwd;");
        string sqlQuery = "select whatever from TheTable where MyRestriction = " + incomingID;
        bool HaveYouFoundItYet = false;
        int TrackMyPositionInTheList = 0;
        string queryResults = string.Empty;

        while (!HaveYouFoundItYet && TrackMyPositionInTheList < dbConnStrings.Count)//while you haven't found it and there are still DBs to look into
        {
            using (OleDbConnection currentConnection = new OleDbConnection(dbConnStrings[TrackMyPositionInTheList]))//look into the DB determined by the PositionTracker
            {
                currentConnection.Open();
                OleDbCommand command = new OleDbCommand(sqlQuery, currentConnection);

                if (command.ExecuteScalar() != null)//if you found what you're looking for
                {
                    queryResults = command.ExecuteScalar().ToString();//do whatever with your pulled data
                    HaveYouFoundItYet = true;//make the while loop stop
                }
                else
                {
                    TrackMyPositionInTheList++;//Lets increment the PositionTracker by 1 and look again.
                }
            }
        }

        return queryResults;
    }

修改的这可能是更快的方式

    /// <summary>
    /// this way should be faster than the previous one
    /// because we won't connect to the same DB more than once.
    /// </summary>
    public Form1()
    {
        InitializeComponent();
        //string textThatWouldBeInATextBoxOnTheUserInterface = "30439,30447,32273,32270";//lets pretend this is the textbox value entered by the user
        string textThatWouldBeInATextBoxOnTheUserInterface = "30439,30447,32273";//lets pretend this is the textbox value entered by the user

        Dictionary<string, string> DictionaryOfResults = new Dictionary<string, string>();
        DictionaryOfResults = getTheDataLoopingThroughIDs(textThatWouldBeInATextBoxOnTheUserInterface);
    }

    private Dictionary<string, string> getTheDataLoopingThroughIDs(string incomingIDs)
    {
        Dictionary<string, string> incomingIDsTracker = new Dictionary<string, string>();//something to keep track of the incomingIDs
        foreach (string item in incomingIDs.Replace(" ", "").Split(','))
        {
            incomingIDsTracker.Add(item, null);//add all the ids(keys) to the dictionary, and give them a null value to start
        }

        //lets build the list of DBs we can connect to
        List<string> dbConnStrings = new List<string>();
        dbConnStrings.Add(@"Provider=SQLOLEDB;Server=Server\Schema;Database=dbName1;User Id=uid;Password=pwd;");
        dbConnStrings.Add(@"Provider=SQLOLEDB;Server=Server\Schema;Database=dbName2;User Id=uid;Password=pwd;");
        int TrackMyPositionInTheList = 0;//keep track of how many DBs you connected to

        while (incomingIDsTracker.ContainsValue(null) && TrackMyPositionInTheList < dbConnStrings.Count)//while there are values we haven't found yet, and while there are still DBs to connect to
        {
            using (OleDbConnection currentConnection = new OleDbConnection(dbConnStrings[TrackMyPositionInTheList]))//look into the DB determined by the PositionTracker
            {
                Dictionary<string, string> tempdict = new Dictionary<string, string>();
                tempdict = incomingIDsTracker.Where(p => p.Value == null).ToDictionary(p => p.Key, p => p.Value);//make a temp dictionary of only the keys with null values
                string idstolookfor = string.Join(",", tempdict.Keys);//make that into a comma separated list that we can use in our sql query
                string sqlQuery = "select dialid, docid from dial where dialid in (" + idstolookfor + ")";
                currentConnection.Open();
                OleDbCommand command = new OleDbCommand(sqlQuery, currentConnection);

                if (command.ExecuteScalar() != null)//if you found something
                {
                    OleDbDataReader reader = command.ExecuteReader();
                    while (reader.Read())
                    {
                        incomingIDsTracker[reader["DialId"].ToString()] = reader["docid"].ToString();
                    }
                }
                TrackMyPositionInTheList++;//Lets increment the PositionTracker by 1 and look again.
            }
        }
        return incomingIDsTracker;
    }

Answer 2

您可以对CancellationToken使用async / await。启动多个同时发生的异步请求，当一个返回结果时取消其他请求。例如：

Sub CheckWord()


Dim arrVar As Variant
Dim ws As Worksheet
Dim strCheck As Range

Set arrVar = ActiveWorkbook.Worksheets
'MsgBox (arrVar)

For Each ws In arrVar
   If ws.Range("C9:G20").Value = "Word" Then
    MsgBox (True)
   End If
Next ws

End Sub

Answer 3

您可以使用三部分名称

Select col from db1.dbo.table2 where guid = 'xxx'
union  
Select col from db2.dbo.table2 where guid = 'xxx'

如何使用C＃从Same Server中的多个数据库获取数据？

3 个答案: