使用Command执行存储过程
关键字: 数据库, 存储过程, 参数传递
在数据驱动的应用程序中，存储过程可以提供很多优点。使用存储过程可以将数据库操作封装到一条简单的命令中，可以优化效能，可以增强安全性。只需要按照SQL语法在存储过程名后面跟带参数就可以调用该存储过程。使用ADO.NET中Command对象的Parameters属性你还可以明确的定义和使用output参数和return值。
调用存储过程时，要设置Command对象的CommandType属性为StoreProcedure。一旦设定了CommandType属性为StoreProcedure，你就可以使用Parameters集合来定义参数，就像下面的例子。
注意 使用OdbcCommand调用存储过程时要求提供完整的ODBC CALL语法。
SqlClient
[Visual Basic]
Dim nwindConn As SqlConnection = New SqlConnection("Data Source=localhost;Integrated Security=SSPI;" & _
"Initial Catalog=northwind")
Dim salesCMD As SqlCommand = New SqlCommand("SalesByCategory", nwindConn)
salesCMD.CommandType = CommandType.StoredProcedure
Dim myParm As SqlParameter = salesCMD.Parameters.Add("@CategoryName", SqlDbType.NVarChar, 15)
myParm.Value = "Beverages"
nwindConn.Open()
Dim myReader As SqlDataReader = salesCMD.ExecuteReader()
Console.WriteLine("{0}, {1}", myReader.GetName(0), myReader.GetName(1))
Do While myReader.Read()
Console.WriteLine("{0}, ${1}", myReader.GetString(0), myReader.GetDecimal(1))
Loop
myReader.Close()
nwindConn.Close()
[C#]
SqlConnection nwindConn = new SqlConnection("Data Source=localhost;Integrated Security=SSPI;Initial Catalog=northwind");
SqlCommand salesCMD = new SqlCommand("SalesByCategory", nwindConn);
salesCMD.CommandType = CommandType.StoredProcedure;
SqlParameter myParm = salesCMD.Parameters.Add("@CategoryName", SqlDbType.NVarChar, 15);
myParm.Value = "Beverages";
nwindConn.Open();
SqlDataReader myReader = salesCMD.ExecuteReader();
Console.WriteLine("{0}, {1}", myReader.GetName(0), myReader.GetName(1));
while (myReader.Read())
{
Console.WriteLine("{0}, ${1}", myReader.GetString(0), myReader.GetDecimal(1));
}
myReader.Close();
nwindConn.Close();
OleDb
[Visual Basic]
Dim nwindConn As OleDbConnection = New OleDbConnection("Provider=SQLOLEDB;Data Source=localhost;Integrated Security=SSPI;" & _
"Initial Catalog=northwind")
Dim salesCMD As OleDbCommand = New OleDbCommand("SalesByCategory", nwindConn)
salesCMD.CommandType = CommandType.StoredProcedure
Dim myParm As OleDbParameter = salesCMD.Parameters.Add("@CategoryName", OleDbType.VarChar, 15)
myParm.Value = "Beverages"
nwindConn.Open()
Dim myReader As OleDbDataReader = salesCMD.ExecuteReader()
Console.WriteLine("{0}, {1}", myReader.GetName(0), myReader.GetName(1))
Do While myReader.Read()
Console.WriteLine("{0}, ${1}", myReader.GetString(0), myReader.GetDecimal(1))
Loop
myReader.Close()
nwindConn.Close()
[C#]
OleDbConnection nwindConn = new OleDbConnection("Provider=SQLOLEDB;Data Source=localhost;Integrated Security=SSPI;" +
"Initial Catalog=northwind");
OleDbCommand salesCMD = new OleDbCommand("SalesByCategory", nwindConn);
salesCMD.CommandType = CommandType.StoredProcedure;
OleDbParameter myParm = salesCMD.Parameters.Add("@CategoryName", OleDbType.VarChar, 15);
myParm.Value = "Beverages";
nwindConn.Open();
OleDbDataReader myReader = salesCMD.ExecuteReader();
Console.WriteLine("\t{0}, {1}", myReader.GetName(0), myReader.GetName(1));
while (myReader.Read())
{
Console.WriteLine("\t{0}, ${1}", myReader.GetString(0), myReader.GetDecimal(1));
}
myReader.Close();
nwindConn.Close();
Odbc
[Visual Basic]
Dim nwindConn As OdbcConnection = New OdbcConnection("Driver={SQL Server};Server=localhost;Trusted_Connection=yes;" & _
"Database=northwind")
nwindConn.Open()
Dim salesCMD As OdbcCommand = New OdbcCommand("{ CALL SalesByCategory(?) }", nwindConn)
salesCMD.CommandType = CommandType.StoredProcedure
Dim myParm As OdbcParameter = salesCMD.Parameters.Add("@CategoryName", OdbcType.VarChar, 15)
myParm.Value = "Beverages"
Dim myReader As OdbcDataReader = salesCMD.ExecuteReader()
Console.WriteLine("{0}, {1}", myReader.GetName(0), myReader.GetName(1))
Do While myReader.Read()
Console.WriteLine("{0}, ${1}", myReader.GetString(0), myReader.GetDecimal(1))
Loop
myReader.Close()
nwindConn.Close()
[C#]
OdbcConnection nwindConn = new OdbcConnection("Driver={SQL Server};Server=localhost;Trusted_Connection=yes;" +
"Database=northwind");
nwindConn.Open();
OdbcCommand salesCMD = new OdbcCommand("{ CALL SalesByCategory(?) }", nwindConn);
salesCMD.CommandType = CommandType.StoredProcedure;
OdbcParameter myParm = salesCMD.Parameters.Add("@CategoryName", OdbcType.VarChar, 15);
myParm.Value = "Beverages";
OdbcDataReader myReader = salesCMD.ExecuteReader();
Console.WriteLine("\t{0}, {1}", myReader.GetName(0), myReader.GetName(1));
while (myReader.Read())
{
Console.WriteLine("\t{0}, ${1}", myReader.GetString(0), myReader.GetDecimal(1));
}
myReader.Close();
nwindConn.Close();
一个Parameter对象可以使用Parameter构造器创建，也可以通过调用Command对象的Parameters集合的Add方法创建。Parameters.Add方法的输入参数可以和构造器相同，也可以使用一个存在的Parameter对象。用System.DBNull.Value设置Parameter的值为空。
如果要设置Parameter为非一般的输入参数时，必须设置ParameterDirection属性为InputOutput，Output，或者ReturnValue。下面的例子演示了创建Input, Output, 和 ReturnValue参数的差别。
SqlClient
[Visual Basic]
Dim sampleCMD As SqlCommand = New SqlCommand("SampleProc", nwindConn)
sampleCMD.CommandType = CommandType.StoredProcedure
Dim sampParm As SqlParameter = sampleCMD.Parameters.Add("RETURN_VALUE", SqlDbType.Int)
sampParm.Direction = ParameterDirection.ReturnValue
sampParm = sampleCMD.Parameters.Add("@InputParm", SqlDbType.NVarChar, 12)
sampParm.Value = "Sample Value"
sampParm = sampleCMD.Parameters.Add("@OutputParm", SqlDbType.NVarChar, 28)
sampParm.Direction = ParameterDirection.Output
nwindConn.Open()
Dim sampReader As SqlDataReader = sampleCMD.ExecuteReader()
Console.WriteLine("{0}, {1}", sampReader.GetName(0), sampReader.GetName(1))
Do While sampReader.Read()
Console.WriteLine("{0}, {1}", sampReader.GetInt32(0), sampReader.GetString(1))
Loop
sampReader.Close()
nwindConn.Close()
Console.WriteLine(" @OutputParm: {0}", sampleCMD.Parameters("@OutputParm").Value)
Console.WriteLine("RETURN_VALUE: {0}", sampleCMD.Parameters("RETURN_VALUE").Value)
[C#]
SqlCommand sampleCMD = new SqlCommand("SampleProc", nwindConn);
sampleCMD.CommandType = CommandType.StoredProcedure;
SqlParameter sampParm = sampleCMD.Parameters.Add("RETURN_VALUE", SqlDbType.Int);
sampParm.Direction = ParameterDirection.ReturnValue;
sampParm = sampleCMD.Parameters.Add("@InputParm", SqlDbType.NVarChar, 12);
sampParm.Value = "Sample Value";
sampParm = sampleCMD.Parameters.Add("@OutputParm", SqlDbType.NVarChar, 28);
sampParm.Direction = ParameterDirection.Output;
nwindConn.Open();
SqlDataReader sampReader = sampleCMD.ExecuteReader();
Console.WriteLine("{0}, {1}", sampReader.GetName(0), sampReader.GetName(1));
while (sampReader.Read())
{
Console.WriteLine("{0}, {1}", sampReader.GetInt32(0), sampReader.GetString(1));
}
sampReader.Close();
nwindConn.Close();
Console.WriteLine(" @OutputParm: {0}", sampleCMD.Parameters["@OutputParm"].Value);
Console.WriteLine("RETURN_VALUE: {0}", sampleCMD.Parameters["RETURN_VALUE"].Value);
OleDb
[Visual Basic]
Dim sampleCMD As OleDbCommand = New OleDbCommand("SampleProc", nwindConn)
sampleCMD.CommandType = CommandType.StoredProcedure
Dim sampParm As OleDbParameter = sampleCMD.Parameters.Add("RETURN_VALUE", OleDbType.Integer)
sampParm.Direction = ParameterDirection.ReturnValue
sampParm = sampleCMD.Parameters.Add("@InputParm", OleDbType.VarChar, 12)
sampParm.Value = "Sample Value"
sampParm = sampleCMD.Parameters.Add("@OutputParm", OleDbType.VarChar, 28)
sampParm.Direction = ParameterDirection.Output
nwindConn.Open()
Dim sampReader As OleDbDataReader = sampleCMD.ExecuteReader()
Console.WriteLine("{0}, {1}", sampReader.GetName(0), sampReader.GetName(1))
Do While sampReader.Read()
Console.WriteLine("{0}, {1}", sampReader.GetInt32(0), sampReader.GetString(1))
Loop
sampReader.Close()
nwindConn.Close()
Console.WriteLine(" @OutputParm: {0}", sampleCMD.Parameters("@OutputParm").Value)
Console.WriteLine("RETURN_VALUE: {0}", sampleCMD.Parameters("RETURN_VALUE").Value)
[C#]
OleDbCommand sampleCMD = new OleDbCommand("SampleProc", nwindConn);
sampleCMD.CommandType = CommandType.StoredProcedure;
OleDbParameter sampParm = sampleCMD.Parameters.Add("RETURN_VALUE", OleDbType.Integer);
sampParm.Direction = ParameterDirection.ReturnValue;
sampParm = sampleCMD.Parameters.Add("@InputParm", OleDbType.VarChar, 12);
sampParm.Value = "Sample Value";
sampParm = sampleCMD.Parameters.Add("@OutputParm", OleDbType.VarChar, 28);
sampParm.Direction = ParameterDirection.Output;
nwindConn.Open();
OleDbDataReader sampReader = sampleCMD.ExecuteReader();
Console.WriteLine("{0}, {1}", sampReader.GetName(0), sampReader.GetName(1));
while (sampReader.Read())
{
Console.WriteLine("{0}, {1}", sampReader.GetInt32(0), sampReader.GetString(1));
}
sampReader.Close();
nwindConn.Close();
Console.WriteLine(" @OutputParm: {0}", sampleCMD.Parameters["@OutputParm"].Value);
Console.WriteLine("RETURN_VALUE: {0}", sampleCMD.Parameters["RETURN_VALUE"].Value);
Odbc
[Visual Basic]
Dim sampleCMD As OdbcCommand = New OdbcCommand("{ ? = CALL SampleProc(?, ?) }", nwindConn)
sampleCMD.CommandType = CommandType.StoredProcedure
Dim sampParm As OdbcParameter = sampleCMD.Parameters.Add("RETURN_VALUE", OdbcType.Int)
sampParm.Direction = ParameterDirection.ReturnValue
sampParm = sampleCMD.Parameters.Add("@InputParm", OdbcType.VarChar, 12)
sampParm.Value = "Sample Value"
sampParm = sampleCMD.Parameters.Add("@OutputParm", OdbcType.VarChar, 28)
sampParm.Direction = ParameterDirection.Output
nwindConn.Open()
Dim sampReader As OdbcDataReader = sampleCMD.ExecuteReader()
Console.WriteLine("{0}, {1}", sampReader.GetName(0), sampReader.GetName(1))
Do While sampReader.Read()
Console.WriteLine("{0}, {1}", sampReader.GetInt32(0), sampReader.GetString(1))
Loop
sampReader.Close()
nwindConn.Close()
Console.WriteLine(" @OutputParm: {0}", sampleCMD.Parameters("@OutputParm").Value)
Console.WriteLine("RETURN_VALUE: {0}", sampleCMD.Parameters("RETURN_VALUE").Value)
[C#]
OdbcCommand sampleCMD = new OdbcCommand("{ ? = CALL SampleProc(?, ?) }", nwindConn);
sampleCMD.CommandType = CommandType.StoredProcedure;
OdbcParameter sampParm = sampleCMD.Parameters.Add("RETURN_VALUE", OdbcType.Int);
sampParm.Direction = ParameterDirection.ReturnValue;
sampParm = sampleCMD.Parameters.Add("@InputParm", OdbcType.VarChar, 12);
sampParm.Value = "Sample Value";
sampParm = sampleCMD.Parameters.Add("@OutputParm", OdbcType.VarChar, 28);
sampParm.Direction = ParameterDirection.Output;
nwindConn.Open();
OdbcDataReader sampReader = sampleCMD.ExecuteReader();
Console.WriteLine("{0}, {1}", sampReader.GetName(0), sampReader.GetName(1));
while (sampReader.Read())
{
Console.WriteLine("{0}, {1}", sampReader.GetInt32(0), sampReader.GetString(1));
}
sampReader.Close();
nwindConn.Close();
Console.WriteLine(" @OutputParm: {0}", sampleCMD.Parameters["@OutputParm"].Value);
Console.WriteLine("RETURN_VALUE: {0}", sampleCMD.Parameters["RETURN_VALUE"].Value);
在SqlCommand中使用参数
在SqlCommand中使用参数时，参数的名字必须和存储过程中相应参数的名字匹配。SQL SERVER的.NET Framework Data Provider将存储过程中的参数视为命名参数并且搜索与之匹配的参数标记。
SQL SERVER的.NET Framework Data Provider不支持使用问号标记（?）作为占位符来向SQL语句或者存储过程传递参数。既然如此，你必须命名参数，就下面一样：
SELECT * FROM Customers WHERE CustomerID = @CustomerID
在OleDbCommand 和OdbcCommand中使用参数
在OleDbCommand或者OdbcCommand中使用参数时，参数添加到Parameters集合中的顺序必须和存储过程中参数定义的顺序匹配。OLE DB和ODBC的.NET Framework数据供应程序将存储过程的参数视为占位符，按照顺序来给参数赋值。另外，返回参数必须是第一个被加入到Parameters集合中的参数。
OLE DB和ODBC的.NET Framework数据供应程序不提供使用命名参数来向SQL语句或存储过程传递参数。为此，你必须使用问号(?)占位符，就像下面一样：
SELECT * FROM Customers WHERE CustomerID = ?
因此，向 Parameters 集合添加 Parameter 对象的顺序必须直接对应于该参数的问号占位符的位置。
导出参数信息
参数也可以使用 CommandBuilder 类从存储过程导出。SqlCommandBuilder 和 OleDbCommandBuilder 类都提供了静态方法 DeriveParameters，该静态方法将自动使用存储过程中的参数信息填充 Command 对象的 Parameters 集合。请注意，DeriveParameters 将改写 Command 的任何现有参数信息。
导出参数信息时需要经历一个到数据源的附加行程，以获取参数信息。如果参数信息在设计时是已知的，则可以通过显式设置参数来提高应用程序的性能。
以下代码示例显示如何使用 CommandBuilder.DeriveParameters 来填充 Command 对象的 Parameters 集合。
[Visual Basic]
Dim nwindConn As SqlConnection = New SqlConnection("Data Source=localhost;Initial Catalog=Northwind;Integrated Security=SSPI;")
Dim salesCMD As SqlCommand = New SqlCommand("Sales By Year", nwindConn)
salesCMD.CommandType = CommandType.StoredProcedure
nwindConn.Open()
SqlCommandBuilder.DeriveParameters(salesCMD)
nwindConn.Close()
[C#]
SqlConnection nwindConn = new SqlConnection("Data Source=localhost;Initial Catalog=Northwind;Integrated Security=SSPI;");
SqlCommand salesCMD = new SqlCommand("Sales By Year", nwindConn);
salesCMD.CommandType = CommandType.StoredProcedure;
nwindConn.Open();
SqlCommandBuilder.DeriveParameters(salesCMD);
nwindConn.Close();