SqlCommand Klasse

Definition

public ref class SqlCommand sealed : System::Data::Common::DbCommand, ICloneable

public sealed class SqlCommand : System.Data.Common.DbCommand, ICloneable

type SqlCommand = class
    inherit DbCommand
    interface ICloneable

Public NotInheritable Class SqlCommand
Inherits DbCommand
Implements ICloneable

Vererbung

DbCommand

SqlCommand

Implementiert

ICloneable

Beispiele

Im folgenden Beispiel wird ein SqlConnection, a SqlCommandund a SqlDataReader. Im Beispiel werden die Daten gelesen und in die Konsole geschrieben. Schließlich wird das Beispiel geschlossen SqlDataReader und dann beendet SqlConnection , während er die Using Codeblöcke verlässt.

using System;
using System.Data;
using Microsoft.Data.SqlClient;


namespace SqlCommandCS
{
    class Program
    {
        static void Main()
        {
            string str = "Data Source=(local);Initial Catalog=Northwind;"
                + "Integrated Security=SSPI";
            ReadOrderData(str);

        }

        private static void ReadOrderData(string connectionString)
        {
            string queryString =
                "SELECT OrderID, CustomerID FROM dbo.Orders;";
            using (SqlConnection connection = new SqlConnection(
                       connectionString))
            {
                SqlCommand command = new SqlCommand(
                    queryString, connection);
                connection.Open();
                using (SqlDataReader reader = command.ExecuteReader())
                {
                    while (reader.Read())
                    {
                        Console.WriteLine(String.Format("{0}, {1}",
                            reader[0], reader[1]));
                    }
                }
            }
        }

Das folgende Beispiel zeigt, wie verschiedene Typen von SqlCommand-Objekten erstellt und ausgeführt werden.

Zuerst müssen Sie die Beispieldatenbank erstellen, indem Sie das folgende Skript ausführen:

USE [master]
GO

CREATE DATABASE [MySchool]
GO

USE [MySchool]
GO

SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE procedure [dbo].[CourseExtInfo] @CourseId int
as
select c.CourseID,c.Title,c.Credits,d.Name as DepartmentName
from Course as c left outer join Department as d on c.DepartmentID=d.DepartmentID
where c.CourseID=@CourseId

GO

SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
create procedure [dbo].[DepartmentInfo] @DepartmentId int,@CourseCount int output
as
select @CourseCount=Count(c.CourseID)
from course as c
where c.DepartmentID=@DepartmentId

select d.DepartmentID,d.Name,d.Budget,d.StartDate,d.Administrator
from Department as d
where d.DepartmentID=@DepartmentId

GO

SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
Create PROCEDURE [dbo].[GetDepartmentsOfSpecifiedYear]
@Year int,@BudgetSum money output
AS
BEGIN
SELECT @BudgetSum=SUM([Budget])
FROM [MySchool].[dbo].[Department]
Where YEAR([StartDate])=@Year

SELECT [DepartmentID]
,[Name]
,[Budget]
,[StartDate]
,[Administrator]
FROM [MySchool].[dbo].[Department]
Where YEAR([StartDate])=@Year

END
GO

SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE TABLE [dbo].[Course]([CourseID] [nvarchar](10) NOT NULL,
[Year] [smallint] NOT NULL,
[Title] [nvarchar](100) NOT NULL,
[Credits] [int] NOT NULL,
[DepartmentID] [int] NOT NULL,
CONSTRAINT [PK_Course] PRIMARY KEY CLUSTERED
(
[CourseID] ASC,
[Year] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]) ON [PRIMARY]

GO

SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE TABLE [dbo].[Department]([DepartmentID] [int] IDENTITY(1,1) NOT NULL,
[Name] [nvarchar](50) NOT NULL,
[Budget] [money] NOT NULL,
[StartDate] [datetime] NOT NULL,
[Administrator] [int] NULL,
CONSTRAINT [PK_Department] PRIMARY KEY CLUSTERED
(
[DepartmentID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]) ON [PRIMARY]

GO

SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE TABLE [dbo].[Person]([PersonID] [int] IDENTITY(1,1) NOT NULL,
[LastName] [nvarchar](50) NOT NULL,
[FirstName] [nvarchar](50) NOT NULL,
[HireDate] [datetime] NULL,
[EnrollmentDate] [datetime] NULL,
CONSTRAINT [PK_School.Student] PRIMARY KEY CLUSTERED
(
[PersonID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]) ON [PRIMARY]

GO

SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE TABLE [dbo].[StudentGrade]([EnrollmentID] [int] IDENTITY(1,1) NOT NULL,
[CourseID] [nvarchar](10) NOT NULL,
[StudentID] [int] NOT NULL,
[Grade] [decimal](3, 2) NOT NULL,
CONSTRAINT [PK_StudentGrade] PRIMARY KEY CLUSTERED
(
[EnrollmentID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]) ON [PRIMARY]

GO

SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
create view [dbo].[EnglishCourse]
as
select c.CourseID,c.Title,c.Credits,c.DepartmentID
from Course as c join Department as d on c.DepartmentID=d.DepartmentID
where d.Name=N'English'

GO
INSERT [dbo].[Course] ([CourseID], [Year], [Title], [Credits], [DepartmentID]) VALUES (N'C1045', 2012, N'Calculus', 4, 7)
INSERT [dbo].[Course] ([CourseID], [Year], [Title], [Credits], [DepartmentID]) VALUES (N'C1061', 2012, N'Physics', 4, 1)
INSERT [dbo].[Course] ([CourseID], [Year], [Title], [Credits], [DepartmentID]) VALUES (N'C2021', 2012, N'Composition', 3, 2)
INSERT [dbo].[Course] ([CourseID], [Year], [Title], [Credits], [DepartmentID]) VALUES (N'C2042', 2012, N'Literature', 4, 2)
SET IDENTITY_INSERT [dbo].[Department] ON

INSERT [dbo].[Department] ([DepartmentID], [Name], [Budget], [StartDate], [Administrator]) VALUES (1, N'Engineering', 350000.0000, CAST(0x0000999C00000000 AS DateTime), 2)
INSERT [dbo].[Department] ([DepartmentID], [Name], [Budget], [StartDate], [Administrator]) VALUES (2, N'English', 120000.0000, CAST(0x0000999C00000000 AS DateTime), 6)
INSERT [dbo].[Department] ([DepartmentID], [Name], [Budget], [StartDate], [Administrator]) VALUES (4, N'Economics', 200000.0000, CAST(0x0000999C00000000 AS DateTime), 4)
INSERT [dbo].[Department] ([DepartmentID], [Name], [Budget], [StartDate], [Administrator]) VALUES (7, N'Mathematics', 250024.0000, CAST(0x0000999C00000000 AS DateTime), 3)
SET IDENTITY_INSERT [dbo].[Department] OFF
SET IDENTITY_INSERT [dbo].[Person] ON

INSERT [dbo].[Person] ([PersonID], [LastName], [FirstName], [HireDate], [EnrollmentDate]) VALUES (1, N'Hu', N'Nan', NULL, CAST(0x0000A0BF00000000 AS DateTime))
INSERT [dbo].[Person] ([PersonID], [LastName], [FirstName], [HireDate], [EnrollmentDate]) VALUES (2, N'Norman', N'Laura', NULL, CAST(0x0000A0BF00000000 AS DateTime))
INSERT [dbo].[Person] ([PersonID], [LastName], [FirstName], [HireDate], [EnrollmentDate]) VALUES (3, N'Olivotto', N'Nino', NULL, CAST(0x0000A0BF00000000 AS DateTime))
INSERT [dbo].[Person] ([PersonID], [LastName], [FirstName], [HireDate], [EnrollmentDate]) VALUES (4, N'Anand', N'Arturo', NULL, CAST(0x0000A0BF00000000 AS DateTime))
INSERT [dbo].[Person] ([PersonID], [LastName], [FirstName], [HireDate], [EnrollmentDate]) VALUES (5, N'Jai', N'Damien', NULL, CAST(0x0000A0BF00000000 AS DateTime))
INSERT [dbo].[Person] ([PersonID], [LastName], [FirstName], [HireDate], [EnrollmentDate]) VALUES (6, N'Holt', N'Roger', CAST(0x000097F100000000 AS DateTime), NULL)
INSERT [dbo].[Person] ([PersonID], [LastName], [FirstName], [HireDate], [EnrollmentDate]) VALUES (7, N'Martin', N'Randall', CAST(0x00008B1A00000000 AS DateTime), NULL)
SET IDENTITY_INSERT [dbo].[Person] OFF
SET IDENTITY_INSERT [dbo].[StudentGrade] ON

INSERT [dbo].[StudentGrade] ([EnrollmentID], [CourseID], [StudentID], [Grade]) VALUES (1, N'C1045', 1, CAST(3.50 AS Decimal(3, 2)))
INSERT [dbo].[StudentGrade] ([EnrollmentID], [CourseID], [StudentID], [Grade]) VALUES (2, N'C1045', 2, CAST(3.00 AS Decimal(3, 2)))
INSERT [dbo].[StudentGrade] ([EnrollmentID], [CourseID], [StudentID], [Grade]) VALUES (3, N'C1045', 3, CAST(2.50 AS Decimal(3, 2)))
INSERT [dbo].[StudentGrade] ([EnrollmentID], [CourseID], [StudentID], [Grade]) VALUES (4, N'C1045', 4, CAST(4.00 AS Decimal(3, 2)))
INSERT [dbo].[StudentGrade] ([EnrollmentID], [CourseID], [StudentID], [Grade]) VALUES (5, N'C1045', 5, CAST(3.50 AS Decimal(3, 2)))
INSERT [dbo].[StudentGrade] ([EnrollmentID], [CourseID], [StudentID], [Grade]) VALUES (6, N'C1061', 1, CAST(4.00 AS Decimal(3, 2)))
INSERT [dbo].[StudentGrade] ([EnrollmentID], [CourseID], [StudentID], [Grade]) VALUES (7, N'C1061', 3, CAST(3.50 AS Decimal(3, 2)))
INSERT [dbo].[StudentGrade] ([EnrollmentID], [CourseID], [StudentID], [Grade]) VALUES (8, N'C1061', 4, CAST(2.50 AS Decimal(3, 2)))
INSERT [dbo].[StudentGrade] ([EnrollmentID], [CourseID], [StudentID], [Grade]) VALUES (9, N'C1061', 5, CAST(1.50 AS Decimal(3, 2)))
INSERT [dbo].[StudentGrade] ([EnrollmentID], [CourseID], [StudentID], [Grade]) VALUES (10, N'C2021', 1, CAST(2.50 AS Decimal(3, 2)))
INSERT [dbo].[StudentGrade] ([EnrollmentID], [CourseID], [StudentID], [Grade]) VALUES (11, N'C2021', 2, CAST(3.50 AS Decimal(3, 2)))
INSERT [dbo].[StudentGrade] ([EnrollmentID], [CourseID], [StudentID], [Grade]) VALUES (12, N'C2021', 4, CAST(3.00 AS Decimal(3, 2)))
INSERT [dbo].[StudentGrade] ([EnrollmentID], [CourseID], [StudentID], [Grade]) VALUES (13, N'C2021', 5, CAST(3.00 AS Decimal(3, 2)))
INSERT [dbo].[StudentGrade] ([EnrollmentID], [CourseID], [StudentID], [Grade]) VALUES (14, N'C2042', 1, CAST(2.00 AS Decimal(3, 2)))
INSERT [dbo].[StudentGrade] ([EnrollmentID], [CourseID], [StudentID], [Grade]) VALUES (15, N'C2042', 2, CAST(3.50 AS Decimal(3, 2)))
INSERT [dbo].[StudentGrade] ([EnrollmentID], [CourseID], [StudentID], [Grade]) VALUES (16, N'C2042', 3, CAST(4.00 AS Decimal(3, 2)))
INSERT [dbo].[StudentGrade] ([EnrollmentID], [CourseID], [StudentID], [Grade]) VALUES (17, N'C2042', 5, CAST(3.00 AS Decimal(3, 2)))
SET IDENTITY_INSERT [dbo].[StudentGrade] OFF
ALTER TABLE [dbo].[Course]  WITH CHECK ADD  CONSTRAINT [FK_Course_Department] FOREIGN KEY([DepartmentID])
REFERENCES [dbo].[Department] ([DepartmentID])
GO
ALTER TABLE [dbo].[Course] CHECK CONSTRAINT [FK_Course_Department]
GO
ALTER TABLE [dbo].[StudentGrade]  WITH CHECK ADD  CONSTRAINT [FK_StudentGrade_Student] FOREIGN KEY([StudentID])
REFERENCES [dbo].[Person] ([PersonID])
GO
ALTER TABLE [dbo].[StudentGrade] CHECK CONSTRAINT [FK_StudentGrade_Student]
GO

Kompilieren und ausführen Sie als Nächstes Folgendes:

using System;
using System.Data;
using Microsoft.Data.SqlClient;
using System.Threading.Tasks;

class Program
{

    static class SqlHelper
    {
        // Set the connection, command, and then execute the command with non query.
        public static Int32 ExecuteNonQuery(String connectionString, String commandText,
        CommandType commandType, params SqlParameter[] parameters)
        {
            using (SqlConnection conn = new SqlConnection(connectionString))
            {
                using (SqlCommand cmd = new SqlCommand(commandText, conn))
                {
                    // There're three command types: StoredProcedure, Text, TableDirect. The TableDirect
                    // type is only for OLE DB.
                    cmd.CommandType = commandType;
                    cmd.Parameters.AddRange(parameters);

                    conn.Open();
                    return cmd.ExecuteNonQuery();
                }
            }
        }

        // Set the connection, command, and then execute the command and only return one value.
        public static Object ExecuteScalar(String connectionString, String commandText,
        CommandType commandType, params SqlParameter[] parameters)
        {
            using (SqlConnection conn = new SqlConnection(connectionString))
            {
                using (SqlCommand cmd = new SqlCommand(commandText, conn))
                {
                    cmd.CommandType = commandType;
                    cmd.Parameters.AddRange(parameters);

                    conn.Open();
                    return cmd.ExecuteScalar();
                }
            }
        }

        // Set the connection, command, and then execute the command with query and return the reader.
        public static SqlDataReader ExecuteReader(String connectionString, String commandText,
        CommandType commandType, params SqlParameter[] parameters)
        {
            SqlConnection conn = new SqlConnection(connectionString);

            using (SqlCommand cmd = new SqlCommand(commandText, conn))
            {
                cmd.CommandType = commandType;
                cmd.Parameters.AddRange(parameters);

                conn.Open();
                // When using CommandBehavior.CloseConnection, the connection will be closed when the
                // IDataReader is closed.
                SqlDataReader reader = cmd.ExecuteReader(CommandBehavior.CloseConnection);

                return reader;
            }
        }
    }

    static void Main(string[] args)
    {
        String connectionString = "Data Source=(local);Initial Catalog=MySchool;Integrated Security=True;";

        CountCourses(connectionString, 2012);
        Console.WriteLine();

        Console.WriteLine("Following result is the departments that started from 2007:");
        GetDepartments(connectionString, 2007);
        Console.WriteLine();

        Console.WriteLine("Add the credits when the credits of course is lower than 4.");
        AddCredits(connectionString, 4);
        Console.WriteLine();

        Console.WriteLine("Please press any key to exit...");
        Console.ReadKey();
    }

    static void CountCourses(String connectionString, Int32 year)
    {
        String commandText = "Select Count([CourseID]) FROM [MySchool].[dbo].[Course] Where Year=@Year";
        SqlParameter parameterYear = new SqlParameter("@Year", SqlDbType.Int);
        parameterYear.Value = year;

        Object oValue = SqlHelper.ExecuteScalar(connectionString, commandText, CommandType.Text, parameterYear);
        Int32 count;
        if (Int32.TryParse(oValue.ToString(), out count))
            Console.WriteLine("There {0} {1} course{2} in {3}.", count > 1 ? "are" : "is", count, count > 1 ? "s" : null, year);
    }

    // Display the Departments that start from the specified year.
    static void GetDepartments(String connectionString, Int32 year)
    {
        String commandText = "dbo.GetDepartmentsOfSpecifiedYear";

        // Specify the year of StartDate
        SqlParameter parameterYear = new SqlParameter("@Year", SqlDbType.Int);
        parameterYear.Value = year;

        // When the direction of parameter is set as Output, you can get the value after
        // executing the command.
        SqlParameter parameterBudget = new SqlParameter("@BudgetSum", SqlDbType.Money);
        parameterBudget.Direction = ParameterDirection.Output;

        using (SqlDataReader reader = SqlHelper.ExecuteReader(connectionString, commandText,
        CommandType.StoredProcedure, parameterYear, parameterBudget))
        {
            Console.WriteLine("{0,-20}{1,-20}{2,-20}{3,-20}", "Name", "Budget", "StartDate",
            "Administrator");
            while (reader.Read())
            {
                Console.WriteLine("{0,-20}{1,-20:C}{2,-20:d}{3,-20}", reader["Name"],
                reader["Budget"], reader["StartDate"], reader["Administrator"]);
            }
        }
        Console.WriteLine("{0,-20}{1,-20:C}", "Sum:", parameterBudget.Value);
    }

    // If credits of course is lower than the certain value, the method will add the credits.
    static void AddCredits(String connectionString, Int32 creditsLow)
    {
        String commandText = "Update [MySchool].[dbo].[Course] Set Credits=Credits+1 Where Credits<@Credits";

        SqlParameter parameterCredits = new SqlParameter("@Credits", creditsLow);

        Int32 rows = SqlHelper.ExecuteNonQuery(connectionString, commandText, CommandType.Text, parameterCredits);

        Console.WriteLine("{0} row{1} {2} updated.", rows, rows > 1 ? "s" : null, rows > 1 ? "are" : "is");
    }
}

Hinweise

Wenn eine Instanz erstellt SqlCommand wird, werden die Lese-/Schreibeigenschaften auf ihre Anfangswerte festgelegt. Eine Liste dieser Werte finden Sie im SqlCommand Konstruktor.

SqlCommand bietet die folgenden Methoden zum Ausführen von Befehlen in einer SQL Server-Datenbank:

Sie können die CommandText Eigenschaft zurücksetzen und das SqlCommand Objekt wiederverwenden. Sie müssen den SqlDataReader Befehl jedoch schließen, bevor Sie einen neuen oder vorherigen Befehl ausführen können.

Wenn eine SqlException von der Methode generiert wird, die eine SqlCommandausführt, bleibt die SqlConnection geöffnet, wenn der Schweregrad 19 oder weniger beträgt. Wenn der Schweregrad 20 oder höher ist, schließt SqlConnectionder Server die . Der Benutzer kann die Verbindung jedoch erneut öffnen und fortfahren.