Tài liệu Using a Single Stored Procedure to Update Multiple Changes to a SQL Server Database pdf

[ Team LiB ]Recipe 8.11 Using a Single Stored Procedure to Update Multiple Changes to a SQL Server Database Problem You need to update a SQL Server 2000 database with changes to multip

[ Team LiB ]

Recipe 8.11 Using a Single Stored Procedure to Update Multiple Changes to a SQL Server Database

Problem

You need to update a SQL Server 2000 database with changes to multiple rows in a

DataSet by executing a single stored procedure

Solution

Use OpenXML with an XMLdocument representing a DataSet of the changes made

The schema of table TBL0811 used in this solution is shown in Table 8-10

Table 8-10 TBL0811 schema

Example 8-16 uses a single stored procedure:

SP0811_Update

Used to update the table TBL0811 with the changes made to the DataSet passed in

as an NText input parameter @data The parameters @data and @datadeleted

contain an XML representation of a DataSet containing all updated and added

records and all deleted records, respectively These parameters are parsed using

the system stored procedure sp_xml_preparedocument that returns a handle that is subsequently used to access the parsed XML document OpenXML is used to

update, insert, and delete the DataSet changes made to TBL0811 Finally, the

system stored procedure sp_xml_removedocument is used to free the memory

used by the parsed XML documents

The sample code contains two event handlers:

Form.Load

Sets up the sample by creating a DataSet containing the contents of the table

TBL0811 The ColumnMapping for each column is set to MappingType.Attribute The default view of the table is bound to the data grid on the form

Update Button.Click

Writes the XML representation of the added and changed records in the DataSet to the stored procedure NText parameter @data and the XML representation of deleted records in the DataSet to the stored procedure NText parameter

@datadelete The stored procedure SP0811_Update is called to update the

database with the batched changes

Example 8-16 Stored procedure: SP0811_Update

ALTER PROC SP0811_Update

@data ntext = null,

@datadelete ntext = null

AS

DECLARE @hDoc int

updated and inserted records

if @data is not null

begin

EXEC sp_xml_preparedocument @hDoc OUTPUT, @data

UPDATE TBL0811

SET

TBL0811.Field1 = XmlTBL0811.Field1,

TBL0811.Field2 = XmlTBL0811.Field2

FROM

OPENXML(@hDoc, 'NewDataSet/TBL0811')

WITH (

Id Integer,

Field1 nvarchar(50),

Field2 nvarchar(50)

) XmlTBL0811

WHERE

TBL0811.Id = XmlTBL0811.Id

INSERT INTO TBL0811

SELECT

Id,

Field1,

Field2

FROM

OPENXML(@hdoc, 'NewDataSet/TBL0811')

WITH (

Id Integer,

Field1 nvarchar(50),

Field2 nvarchar(50)

) XmlTBL0811

WHERE

XmlTBL0811.Id NOT IN (SELECT Id from TBL0811)

EXEC sp_xml_removedocument @hDoc

end

deleted records

if @datadelete is not null

begin

EXEC sp_xml_preparedocument @hDoc OUTPUT, @datadelete

DELETE TBL0811

FROM

TBL0811 INNER JOIN

OPENXML(@hDoc, 'NewDataSet/TBL0811')

WITH (

Id Integer,

Field1 nvarchar(50),

Field2 nvarchar(50)

) XmlTBL0811

ON TBL0811.Id = XmlTBL0811.Id

EXEC sp_xml_removedocument @hDoc

end

The C# code is shown in Example 8-17

Example 8-17 File: StoredProcedureMultipleRowsForm.cs

// Namespaces, variables, and constants

using System;

using System.Configuration;

using System.Windows.Forms;

using System.Text;

using System.IO;

using System.Data;

using System.Data.SqlClient;

private DataSet ds;

private const String TABLENAME = "TBL0811";

private const String STOREDPROCEDURE_NAME = "SP0811_Update";

//

private void StoredProcedureMultipleRowsForm_Load(object sender,

System.EventArgs e)

{

ds = new DataSet( );

// Create the DataAdapter

SqlDataAdapter da = new SqlDataAdapter("SELECT * FROM " + TABLENAME, ConfigurationSettings.AppSettings["Sql_ConnectString"]);

// Load the schema and data for the table

da.FillSchema(ds, SchemaType.Source, TABLENAME);

da.Fill(ds, TABLENAME);

// Columns in XML representation of data as attributes

foreach(DataColumn col in ds.Tables[TABLENAME].Columns)

col.ColumnMapping = MappingType.Attribute;

// This technique supports only update and insert; turn off delete

// records in the default view

ds.Tables[TABLENAME].DefaultView.AllowDelete = false;

// Bind the default view of the table to the grid

dataGrid.DataSource = ds.Tables[TABLENAME].DefaultView;

}

private void updateButton_Click(object sender, System.EventArgs e)

{

StringBuilder sb;

StringWriter sw;

// Create a connection and command for the update stored procedure

SqlConnection conn = new SqlConnection(

ConfigurationSettings.AppSettings["Sql_ConnectString"]);

SqlCommand cmd = new SqlCommand( );

cmd.Connection = conn;

cmd.CommandText = STOREDPROCEDURE_NAME;

cmd.CommandType = CommandType.StoredProcedure;

// Inserted and updated records

if (ds.HasChanges(DataRowState.Added | DataRowState.Modified)) {

sb = new StringBuilder( );

sw = new StringWriter(sb);

ds.GetChanges(

DataRowState.Added | DataRowState.Modified).WriteXml(sw, XmlWriteMode.WriteSchema);

cmd.Parameters.Add("@data", SqlDbType.NText);

cmd.Parameters["@data"].Value = sb.ToString( );

sw.Close( );

}

// Deleted records

if (ds.HasChanges(DataRowState.Deleted))

{

sb = new StringBuilder( );

sw = new StringWriter(sb);

// Get the DataSet containing the records deleted and call

// RejectChanges( ) so that the original version of those rows // are available so that WriteXml( ) works

DataSet dsChange = ds.GetChanges(DataRowState.Deleted); dsChange.RejectChanges( );

dsChange.WriteXml(sw, XmlWriteMode.WriteSchema);

cmd.Parameters.Add("@datadelete", SqlDbType.NText);

cmd.Parameters["@datadelete"].Value = sb.ToString( );

sw.Close( );

}

// Execute the stored procedure

conn.Open( );

cmd.ExecuteNonQuery( );

conn.Close( );

ds.AcceptChanges( );

MessageBox.Show("Update completed.",

"Multiple Row Update/Insert Stored Procedure",

MessageBoxButtons.OK, MessageBoxIcon.Information);

}

Discussion

OpenXML provides a result set view of an XML document allowing you to use the XML document in a T-SQL statement in the same way a result set provider such as a table or view is used

The simple form of the OpenXML command is:

OPENXML(int iDoc, nvarchar rowPattern)

WITH (SchemaDeclaration)

The two input arguments are:

iDoc

The document handle of the internal representation of an XML document created

by using the system stored procedure sp_xml_preparedocument

rowPattern

The XPath query used to select the nodes in the XML document to be processed The argument for the WITH clause is:

SchemaDeclaration

The format of the result set If not supplied, the results are returned in an edge

table format representing the XML document structure in a single table

The system stored procedure sp_xml_preparedocument reads XML as input text using the MSXML parser and returns a handle that you can use to access the internal

representation of the XML document The handle is valid for the duration of the

connection to the SQL Server or until it is reset The handle can be invalidated and the associated memory freed by calling the system stored procedure

sp_xml_removedocument The syntax of the stored procedure is:

sp_xml_preparedocument hDoc OUTPUT, [xmlText], [xpathNamespaces]

The arguments are:

hDoc

An integer parameter that returns a handle to the internal representation of the XML document

xmlText

A text parameter that specifies the original XML document The default value is null which results in the return of a handle to an internal representation to an empty XML document

xpathNamespaces

A text parameter that specifies the namespace declarations used in row and column XPath expressions in OpenXML The default value is:

<root xmlns:mp="urn:schemas-microsoft-com:xml-metaprop">

The system stored procedure sp_xml_removedocument removes the internal representation of an XML document specified by a document handle obtained from the system stored procedure sp_xml_preparedocument and invalidates the handle The syntax of the stored procedure is:

sp_xml_removedocument hDoc

The argument is:

hDoc

An integer parameter that returns a handle to the internal representation of the XML document

For more information about the OpenXML command and the system stored procedures sp_xml_preparedocument and sp_xml_removedocuemnt, see Microsoft SQL Server Books Online

[ Team LiB ]