SqlCommand Clase

Definición

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

public ref class SqlCommand sealed : System::ComponentModel::Component, ICloneable, IDisposable, System::Data::IDbCommand

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

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

public sealed class SqlCommand : System.ComponentModel.Component, ICloneable, IDisposable, System.Data.IDbCommand

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

type SqlCommand = class
    inherit DbCommand

type SqlCommand = class
    inherit Component
    interface IDbCommand
    interface IDisposable
    interface ICloneable

type SqlCommand = class
    inherit DbCommand
    interface ICloneable

Public NotInheritable Class SqlCommand
Inherits DbCommand

Public NotInheritable Class SqlCommand
Inherits Component
Implements ICloneable, IDbCommand, IDisposable

Public NotInheritable Class SqlCommand
Inherits DbCommand
Implements ICloneable

Herencia

Object

DbCommand

SqlCommand

Herencia

Object

MarshalByRefObject

Component

DbCommand

SqlCommand

Herencia

Object

MarshalByRefObject

Component

SqlCommand

Implementaciones

IDbCommand ICloneable IDisposable

Ejemplos

En el ejemplo siguiente se crea un SqlConnectionobjeto , y SqlCommand.SqlDataReader En el ejemplo se leen los datos y se escribe en la consola. Por último, el ejemplo cierra SqlDataReader y, a continuación, a SqlConnection medida que sale de los bloques de Using código.

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]));
            }
        }
    }
}

Public Sub ReadOrderData(ByVal connectionString As String)
    Dim queryString As String = _
        "SELECT OrderID, CustomerID FROM dbo.Orders;"
    Using connection As New SqlConnection(connectionString)
        Dim command As New SqlCommand(queryString, connection)
        connection.Open()
        Dim reader As SqlDataReader = command.ExecuteReader()
        Try
            While reader.Read()
                Console.WriteLine(String.Format("{0}, {1}", _
                    reader(0), reader(1)))
            End While
        Finally
            ' Always call Close when done reading.
            reader.Close()
        End Try
    End Using
End Sub

En el ejemplo siguiente se muestra cómo crear y ejecutar diferentes tipos de objetos SqlCommand.

En primer lugar, debe crear la base de datos de ejemplo ejecutando el siguiente script:

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

A continuación, compile y ejecute lo siguiente:

using System;
using System.Data;
using System.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;Asynchronous Processing=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");
   }
}

Comentarios

Cuando se crea una instancia de , las propiedades de SqlCommand lectura y escritura se establecen en sus valores iniciales. Para obtener una lista de estos valores, consulte el SqlCommand constructor .

SqlCommandpresenta los métodos siguientes para ejecutar comandos en una base de datos de SQL Server:

Puede restablecer la CommandText propiedad y reutilizar el SqlCommand objeto . Sin embargo, debe cerrar antes SqlDataReader de poder ejecutar un comando nuevo o anterior.

Si el método genera un SqlException objeto que ejecuta , SqlCommandSqlConnection permanece abierto cuando el nivel de gravedad es 19 o menos. Cuando el nivel de gravedad es 20 o superior, el servidor normalmente cierra .SqlConnection Sin embargo, el usuario puede volver a abrir la conexión y continuar.

Constructores

Propiedades

Métodos

Eventos

Implementaciones de interfaz explícitas

Se aplica a

Consulte también

• Recuperar y modificar datos en ADO.NET
• SQL Server y ADO.NET
• Información general de ADO.NET