SqlCommand 类
定义
重要
一些信息与预发行产品相关,相应产品在发行之前可能会进行重大修改。 对于此处提供的信息,Microsoft 不作任何明示或暗示的担保。
表示要对 SQL Server 数据库执行的一个 Transact-SQL 语句或存储过程。 此类不能被继承。
public ref class SqlCommand sealed : System::Data::Common::DbCommand, ICloneable
public ref class SqlCommand sealed : System::Data::Common::DbCommand
public ref class SqlCommand sealed : System::ComponentModel::Component, ICloneable, IDisposable, System::Data::IDbCommand
public sealed class SqlCommand : 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
type SqlCommand = class
inherit DbCommand
interface ICloneable
type SqlCommand = class
inherit DbCommand
type SqlCommand = class
inherit Component
interface IDbCommand
interface IDisposable
interface ICloneable
Public NotInheritable Class SqlCommand
Inherits DbCommand
Implements ICloneable
Public NotInheritable Class SqlCommand
Inherits DbCommand
Public NotInheritable Class SqlCommand
Inherits Component
Implements ICloneable, IDbCommand, IDisposable
- 继承
- 继承
- 继承
- 实现
示例
以下示例创建 SqlConnection、 SqlCommand和 SqlDataReader。 该示例通读数据,将其写入控制台。 最后,该示例关闭 , SqlDataReader 然后在 SqlConnection 退出 Using
代码块时关闭 。
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
以下示例演示如何创建和执行不同类型的 SqlCommand 对象。
首先,必须通过执行以下脚本来创建示例数据库:
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
接下来,编译并执行以下操作:
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");
}
}
注解
创建 实例 SqlCommand 时,读/写属性设置为其初始值。 有关这些值的列表,请参阅 SqlCommand 构造函数。
SqlCommand具有以下用于在SQL Server数据库上执行命令的方法:
项 | 说明 |
---|---|
BeginExecuteNonQuery | 启动此 SqlCommand描述的 Transact-SQL 语句或存储过程的异步执行,通常执行 INSERT、DELETE、UPDATE 和 SET 语句等命令。 对 的每个调用 BeginExecuteNonQuery 都必须与完成操作的调用配对,该调用 EndExecuteNonQuery 通常在单独的线程上完成操作。 |
BeginExecuteReader | 启动由此 SqlCommand 描述的 Transact-SQL 语句或存储过程的异步执行,并从服务器检索一个或多个结果集。 对 的每个调用 BeginExecuteReader 都必须与完成操作的调用配对,该调用 EndExecuteReader 通常在单独的线程上完成操作。 |
BeginExecuteXmlReader | 启动此 SqlCommand 描述的 Transact-SQL 语句或存储过程的异步执行。 对 的每个调用 BeginExecuteXmlReader 都必须与对 EndExecuteXmlReader 的调用配对,该调用通常会在单独的线程上完成操作,并返回 一个 XmlReader 对象。 |
ExecuteReader | 执行返回行的命令。 为了提高性能, ExecuteReader 使用 Transact-SQL sp_executesql 系统存储过程调用命令。 因此, ExecuteReader 如果用于执行 Transact-SQL SET 语句等命令,则可能不会产生所需的效果。 |
ExecuteNonQuery | 执行 Transact-SQL INSERT、DELETE、UPDATE 和 SET 语句等命令。 |
ExecuteScalar | 检索单个值 (例如,从数据库) 聚合值。 |
ExecuteXmlReader | 将 CommandText 发送到 Connection,并生成一个 XmlReader 对象。 |
可以重置 属性 CommandText 并重用 对象 SqlCommand 。 但是,必须先关闭 , SqlDataReader 然后才能执行新的或上一个命令。
SqlException如果 由执行 的方法生成 ,SqlCommand则 当严重性级别为 19 或更低时, SqlConnection 将保持打开状态。 当严重性级别为 20 或更高时,服务器通常会关闭 SqlConnection。 但是,用户可以重新打开连接并继续操作。
注意
无名称(也称为序号)参数不受 SQL Server .NET Framework 数据提供程序支持。
构造函数
SqlCommand() |
初始化 SqlCommand 类的新实例。 |
SqlCommand(String) |
使用查询的文本初始化 SqlCommand 类的新实例。 |
SqlCommand(String, SqlConnection) |
使用查询的文本和 SqlConnection 初始化 SqlCommand 类的新实例。 |
SqlCommand(String, SqlConnection, SqlTransaction) |
使用查询文本、SqlConnection 以及 SqlTransaction 初始化 SqlCommand 类的新实例。 |
SqlCommand(String, SqlConnection, SqlTransaction, SqlCommandColumnEncryptionSetting) |
使用指定的命令文本、连接、事务和加密设置初始化 SqlCommand 类的新实例。 |
属性
方法
事件
Disposed |
在通过调用 Dispose() 方法释放组件时发生。 (继承自 Component) |
StatementCompleted |
当 Transact-SQL 语句执行完成时发生。 |
显式接口实现
ICloneable.Clone() |
创建是当前实例的副本的新 SqlCommand 对象。 |
IDbCommand.Connection |
获取或设置 IDbCommand 的此实例使用的 IDbConnection。 (继承自 DbCommand) |
IDbCommand.CreateParameter() |
创建 SqlParameter 对象的新实例。 |
IDbCommand.CreateParameter() |
创建 IDbDataParameter 对象的新实例。 (继承自 DbCommand) |
IDbCommand.ExecuteReader() |
将 CommandText 发送到 Connection,并生成一个 SqlDataReader。 |
IDbCommand.ExecuteReader() |
对 Connection 执行 CommandText 并生成 IDataReader。 (继承自 DbCommand) |
IDbCommand.ExecuteReader(CommandBehavior) |
将 CommandText 发送到 Connection,并使用 CommandBehavior 值之一生成 SqlDataReader。 |
IDbCommand.ExecuteReader(CommandBehavior) |
对 Connection 执行 CommandText,并使用 CommandBehavior 值之一生成 IDataReader。 (继承自 DbCommand) |
IDbCommand.Parameters | (继承自 DbCommand) |
IDbCommand.Transaction |
获取或设置将在其中执行此 DbCommand 对象的 DbTransaction。 (继承自 DbCommand) |
适用于
另请参阅
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