dotConnect for Oracle入门指南（五）：检索和修改数据

【下载dotConnect for Oracle最新版本】

dotConnect for Oracle(原名OraDirect.NET)创建在ADO.NET技术上，为基于Oracle数据库的应用程序提供完整的解决方案。它为设计应用程序结构带来了新的方法，提升工做效率，使数据库应用程序的开发更简便。

检索和修改数据

• 介绍
• 要求
• 通常信息
• 使用链接的模型检索和更新数据
• 使用断开链接的模型检索和更新数据
• 附加信息

介绍

本教程介绍如何使用OracleCommand、OracleDataReader和OracleDataTable组件。

要求

本教程假设您知道如何链接到服务器，如何在服务器上建立必要的对象，以及如何将数据插入到建立的表中。

请注意，若是您不使用设计时（特别是，若是您不从工具箱放置在设计器或OracleConnection组件上），则必须手动嵌入许可证信息。

通常信息

如咱们所知，任何数据库应用程序的原始功能都是创建到数据源的链接，并处理其中包含的数据。ADO.NET的.NET框架数据提供程序充当应用程序和数据源之间的桥梁，容许您执行命令以及使用DataReader或DataAdapter检索数据。更新数据涉及到使用命令和数据适配器对象；它还可能涉及使用事务。

让咱们进行一些分类，以便更好地理解ADO.NET模型。使用数据有两种方法：链接和断开链接的模型。您能够使用链接模型的类来创建链接和设置事务、获取数据和更新数据源。这些类直接与数据库交互：oracleProviderFactory、oracleConnection、oracleTransaction、oracleDataAdapter、oracleCommand、oracleParameter和oracleDataReader。

这些对象表示ADO.NET的断开链接的模型，不会当即与数据源进行互操做。这些类提供了脱机处理数据存储的能力：数据集、数据表、数据列、数据行、约束、数据关系、数据视图和数据行视图。

咱们将在示例中使用两个模型中的类。

本教程的目标是从table dept检索和更新数据（适当的DDL/DML脚本位于\Program Files\Devart\dotConnect\Oracle\Samples\tables.sql——用于dotConnect for Oracle的默认路径）。

使用链接的模型检索和更新数据

在本示例中，咱们使用OracleCommand和 OracleDataReader来检索和操做数据。

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69

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();             }         }     } }

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59

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

使用断开链接的模型检索和更新数据

使用数据表和数据集的传统方法假定连续建立和初始化链接、命令、数据适配器和commandbuilder对象。Devart OracleDataTable和OracleDataset具备高级功能，能够更轻松地处理数据。更重要的是，使用咱们的组件，您能够在设计时检索和操做数据。

下面是一个演示OracleDataTable用法的小示例。

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36

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;      } }

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32

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数据集向导能够轻松建立OracleDataset，并使用Devart数据集管理器进行可视化管理。

附加信息

本教程只介绍处理数据的基本方法。此外，还能够利用存储过程、类型化数据集和ORM解决方案。Dotconnect for Oracle支持LinqConnect和实体框架ORM技术，用于在关系数据库中的不兼容类型系统和面向对象编程语言之间转换数据。这些技术容许您减小面向数据应用程序所需的代码和维护量。