dotConnect for Oracle入門指南（五）：檢索和修改數據

【下載dotConnect for Oracle最新版本】

dotConnect for Oracle(原名OraDirect.NET)創建在ADO.NET技術上，爲基於Oracle數據庫的應用程序提供完整的解決方案。它爲設計應用程序結構帶來了新的方法，提升工做效率，使數據庫應用程序的開發更簡便。

檢索和修改數據

• 介紹
• 要求
• 通常信息
• 使用鏈接的模型檢索和更新數據
• 使用斷開鏈接的模型檢索和更新數據
• 附加信息

介紹

本教程介紹如何使用OracleCommand、OracleDataReader和OracleDataTable組件。

要求

本教程假設您知道如何鏈接到服務器，如何在服務器上建立必要的對象，以及如何將數據插入到建立的表中。

請注意，若是您不使用設計時（特別是，若是您不從工具箱放置在設計器或OracleConnection組件上），則必須手動嵌入許可證信息。

通常信息

如咱們所知，任何數據庫應用程序的原始功能都是創建到數據源的鏈接，並處理其中包含的數據。ADO.NET的.NET框架數據提供程序充當應用程序和數據源之間的橋樑，容許您執行命令以及使用DataReader或DataAdapter檢索數據。更新數據涉及到使用命令和數據適配器對象；它還可能涉及使用事務。

讓咱們進行一些分類，以便更好地理解ADO.NET模型。使用數據有兩種方法：鏈接和斷開鏈接的模型。您能夠使用鏈接模型的類來創建鏈接和設置事務、獲取數據和更新數據源。這些類直接與數據庫交互：oracleProviderFactory、oracleConnection、oracleTransaction、oracleDataAdapter、oracleCommand、oracleParameter和oracleDataReader。

這些對象表示ADO.NET的斷開鏈接的模型，不會當即與數據源進行互操做。這些類提供了脫機處理數據存儲的能力：數據集、數據表、數據列、數據行、約束、數據關係、數據視圖和數據行視圖。

咱們將在示例中使用兩個模型中的類。

本教程的目標是從table dept檢索和更新數據（適當的DDL/DML腳本位於\Program Files\Devart\dotConnect\Oracle\Samples\tables.sql——用於dotConnect for Oracle的默認路徑）。

使用鏈接的模型檢索和更新數據

在本示例中，咱們使用OracleCommand和 OracleDataReader來檢索和操做數據。

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using Devart.Data.Oracle; ... class Program {     void PrintDept(OracleConnection connection)     {         OracleCommand command = connection.CreateCommand();         command.CommandText = "select * from dept";                   // Call the Close method when you are finished using the OracleDataReader         // to use the associated OracleConnection for any other purpose.         // Or put the reader in the using block to call Close implicitly.         using (OracleDataReader reader = command.ExecuteReader())         {             // printing the column names             for (int i = 0; i < reader.FieldCount; i++)                 Console.Write(reader.GetName(i).ToString() + "\t");             Console.Write(Environment.NewLine);             // Always call Read before accesing data             while (reader.Read())             {                 // printing the table content                 for (int i = 0; i < reader.FieldCount; i++)                     Console.Write(reader.GetValue(i).ToString() + "\t");                 Console.Write(Environment.NewLine);             }         }     }           void ModifyDept(OracleConnection connection)     {         OracleCommand command = connection.CreateCommand();         command.CommandText = "UPDATE DEPT SET LOC='VEGAS' WHERE DEPTNO > 20";                   // return value of ExecuteNonQuery (i) is the number of rows affected by the command         int i = command.ExecuteNonQuery();         Console.WriteLine(Environment.NewLine + "Rows in DEPT updated: {0}", i + Environment.NewLine);     }           static void Main(string[] args)     {         using (OracleConnection conn             = new OracleConnection("User Id=Scott;Password=tiger;Data Source=Ora;"))         {             try             {                 conn.Open();                 Program program = new Program();                                   // printing out the Dept table to console                 program.PrintDept(conn);                                   // updating records in Dept                 program.ModifyDept(conn);                                   // printing out the Dept table to console                 program.PrintDept(conn);             }             catch (OracleException ex)             {                 Console.WriteLine("Exception occurs: {0}", ex.Message);             }             finally             {                 Console.ReadLine();             }         }     } }

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Imports Devart.Data.Oracle ... Module Module1     Sub PrintDept(ByVal connection As OracleConnection)         Dim command As OracleCommand = connection.CreateCommand()         command.CommandText = "select * from dept"                   ' Call the Close method when you are finished using the OracleDataReader         ' to use the associated OracleConnection for any other purpose.         ' Or put the reader in the using block to call Close implicitly.         Using reader As OracleDataReader = command.ExecuteReader()             ' printing the column names             For i As Integer = 0 To reader.FieldCount - 1                 Console.Write(reader.GetName(i).ToString() & VbCrlf)             Next i             Console.Write(Environment.NewLine)                           ' Always call Read before accesing data             While reader.Read()                 ' printing the table content                 For i As Integer = 0 To reader.FieldCount - 1                     Console.Write(reader.GetValue(i).ToString() & VbCrlf)                 Next                 Console.Write(Environment.NewLine)             End While         End Using     End Sub       Sub ModifyDept(ByVal connection As OracleConnection)         Dim command As OracleCommand = connection.CreateCommand()         command.CommandText = "UPDATE DEPT SET LOC='VEGAS' WHERE DEPTNO > 20"                   ' return value of ExecuteNonQuery (i) is the number of rows affected by the command         Dim i As Integer = command.ExecuteNonQuery()         Console.WriteLine(Environment.NewLine & "Rows in DEPT updated: {0}", i & Environment.NewLine)     End Sub       Sub Main()         Using conn _             As New OracleConnection("User Id=Scott;Password=tiger;Data Source=Ora;")             Try                 conn.Open()                                   ' printing out the Dept table to console                 Module1.PrintDept(conn)                                   ' updating records in Dept                 Module1.ModifyDept(conn)                                   ' printing out the Dept table to console                 Module1.PrintDept(conn)             Catch ex As OracleException                 Console.WriteLine("Exception occurs: {0}", ex.Message)             Finally                 Console.ReadLine()             End Try         End Using     End Sub End Module

使用斷開鏈接的模型檢索和更新數據

使用數據表和數據集的傳統方法假定連續建立和初始化鏈接、命令、數據適配器和commandbuilder對象。Devart OracleDataTable和OracleDataset具備高級功能，能夠更輕鬆地處理數據。更重要的是，使用咱們的組件，您能夠在設計時檢索和操做數據。

下面是一個演示OracleDataTable用法的小示例。

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public void UseDataTable() {    OracleDataTable myDataTable     = new OracleDataTable("SELECT * FROM Dept", "User Id=Scott;Password=tiger;Data Source=Ora;");    try    {        // FetchAll=true means to retrieve data from server entirely when DataTable is opened.        //  By default, FetchAll is set to false - only minimal quantity of rows is requested at once,        //  which leads to better initial response time and less network traffic.        myDataTable.FetchAll = true;               // populating DataTable with data from data source        myDataTable.Active = true;               // modifying the third record        myDataTable.Rows[3]["DName"] = "Researches";               // Update method executes the appropriate commands (delete, insert, or update) in the data source.        Console.WriteLine(myDataTable.Update() + " rows updated.");                 // printing the DataTable content        foreach (DataRow myRow in myDataTable.Rows)        {           foreach (DataColumn myCol in myDataTable.Columns)           {               Console.Write(myRow[myCol] + "\t");           }           Console.WriteLine();        }      }      finally      {         //Active=false does not clear the data, but frees the resources allocated on the server, if any.         myDataTable.Active = false;      } }

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Public Sub UseDataTable()     Dim myDataTable As OracleDataTable _         As New OracleDataTable("SELECT * FROM Dept", "User Id=Scott;Password=tiger;Data Source=Ora;")     Try         ' FetchAll=true means to retrieve data from server entirely when DataTable is opened.         '  By default, FetchAll is set to false - only minimal quantity of rows is requested at once,         '  which leads to better initial response time and less network traffic.         myDataTable.FetchAll = True                   ' populating DataTable with data from data source         myDataTable.Active = True                   ' modifying the third record         myDataTable.Rows(3)("DName") = "Researches"                   ' Update method executes the appropriate commands (delete, insert, or update) in the data source.         Console.WriteLine(myDataTable.Update() & " rows updated.")         Dim myRow As DataRow         Dim myCol As DataColumn                   ' printing the DataTable content         For Each myRow In myDataTable.Rows             For Each myCol In myDataTable.Columns                 Console.Write(myRow(myCol) & VbCrlf)             Next myCol             Console.WriteLine()         Next myRow     Finally         ' Active=false does not clear the data, but frees the resources allocated on the server, if any.         myDataTable.Active = False     End Try End Sub

使用Devart數據集嚮導能夠輕鬆建立OracleDataset，並使用Devart數據集管理器進行可視化管理。

附加信息

本教程只介紹處理數據的基本方法。此外，還能夠利用存儲過程、類型化數據集和ORM解決方案。Dotconnect for Oracle支持LinqConnect和實體框架ORM技術，用於在關係數據庫中的不兼容類型系統和麪向對象編程語言之間轉換數據。這些技術容許您減小面向數據應用程序所需的代碼和維護量。