Tài liệu Updating a DataSet with a Many-to-Many Relationship ppt

The stored procedure returns the ChildId value generated by the data source as both an output parameter and in the first returned record.. The stored procedure returns the ParentId value

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Recipe 4.10 Updating a DataSet with a Many-to-Many Relationship

Problem

You have a DataSet that contains two tables that have a many-to-many relationship

between them using a third junction table You get referential integrity errors when you try to update changes to the data in this DataSet back to the data source You need to do this successfully

Solution

Use the techniques described in the discussion

The schema of table TBL0410Parent used in this solution is shown in Table 4-5

Table 4-5 TBL0410Parent schema

The schema of table TBL0410Child used in this solution is shown in Table 4-6

Table 4-6 TBL0410Child schema

The schema of table TBL0410ParentChild used in this solution is shown in Table 4-7

Table 4-7 TBL0410ParentChild schema

ChildId int 4 No

The solution uses eleven stored procedures described in Table 4-8

Table 4-8 Stored procedures for solution in Recipe 4.10

Name Description

SP0410_DeleteChild Deletes the Child record specified by the ChildId input

parameter

SP0410_DeleteParent Deletes the Parent record specified by the ParentId input

parameter

SP0410_DeleteParentChild Deletes the ParentChild record specified by the ParentId

and ChildId input parameters

SP0410_GetChild

Gets the Child record corresponding to the ChildId specified or returns all Child records if no ChildId is specified

SP0410_GetParent

Gets the Parent record corresponding to the ParentId specified or returns all Parent records if no ParentId is specified

SP0410_GetParentChild

Gets the ParentChild records corresponding to the ParentId specified or returns all ParentChild records if no ParentId

is specified

SP0410_InsertChild

Adds a new Child record The stored procedure returns the ChildId value generated by the data source as both an output parameter and in the first returned record

SP0410_InsertParent

Adds a new Parent record The stored procedure returns the ParentId value generated by the data source as both an output parameter and in the first returned record

SP0410_InsertParentChild Adds a new ParentChild record

SP0410_UpdateChild Updates the Child record matching the specified ChildId

SP0410_UpdateParent Updates the Parent record matching the specified ParentId

The sample code contains five event handlers and four methods:

Form.Load

This event handler sets up the sample by creating a DataSet containing a parent,

child, and many-to-many junction table, as well as the DataRelation objects

between them A DataAdapter object is created for each table and the stored

procedures to select, delete, insert, and update records in the data source are

specified for each The LoadData( ) method is called to retrieve data for each table

in the DataSet Finally, the default view for the parent and the child tables are bound to data grids on the form

LoadData( )

This method calls the Fill( ) method of the DataAdapter for each of the parent, child, and junction tables

CreateData( )

This method creates random data in both the parent and child tables and randomly creates relationships between them by adding records to the junction table

UpdateData( )

This method updates all changes in the DataSet back to the data source by calling

in the correct order the Update( ) method of the DataAdapter object for subsets of the data in each of the parent, child, and junction tables

Create Button.Click

This event handler calls the CreateData( ) method to add random data to the

DataSet

Modify Button.Click

This event handler makes random changes to the data in the DataSet:

• Rows from the parent and child table are deleted or have values in their

fields modified

• Parent/child relationships are eliminated by deleting records from the

junction table

• The CreateData( ) method is called to create new data

• The UpdateData( ) method is called to update all of the changes made to the

DataSet with the data source

Delete Button.Click

This event handler deletes all data from the parent, child, and junction table The UpdateData( ) method is called to update the changes made to the DataSet with the

data source

Refresh Button.Click

This event handler clears all data from the DataSet LoadData( ) is then called to load all data from the data source into the parent, child, and junction tables in the DataSet

The 11 stored procedures used in this example are shown in Example 4-13 through Example 4-23

Example 4-13 Stored procedure: SP0410_DeleteChild

CREATE PROCEDURE SP0410_DeleteChild

@ChildId int

AS

SET NOCOUNT ON

delete

from

TBL0410Child

where

ChildId=@ChildId

return 0

Example 4-14 Stored procedure: SP0410_DeleteParent

CREATE PROCEDURE SP0410_DeleteParent

@ParentId int

AS

SET NOCOUNT ON

delete

from

TBL0410Parent

where

ParentId=@ParentId

return 0

Example 4-15 Stored procedure: SP0410_DeleteParentChild

CREATE PROCEDURE SP0410_DeleteParentChild @ParentId int,

@ChildId int

AS

SET NOCOUNT ON

delete

from

TBL0410ParentChild

where

ParentId=@ParentId and

ChildId=@ChildId

return 0

Example 4-16 Stored procedure: SP0410_GetChild

CREATE PROCEDURE SP0410_GetChild

@ChildId int=null

AS

SET NOCOUNT ON

if @ChildId is not null

begin

select

ChildID,

Field3,

Field4

from

TBL0410Child

where

ChildId=@ChildId

return 0

end

select

ChildId,

Field3,

Field4

from

TBL0410Child

return 0

Example 4-17 Stored procedure: SP0410_GetParent

CREATE PROCEDURE SP0410_GetParent

@ParentId int=null

AS

SET NOCOUNT ON

if @ParentId is not null

begin

select

ParentId,

Field1,

Field2

from

TBL0410Parent

where

ParentId=@ParentId

return 0

end

select

ParentId,

Field1,

Field2

from

TBL0410Parent

return 0

Example 4-18 Stored procedure: SP0410_GetParentChild

CREATE PROCEDURE SP0410_GetParentChild

@ParentId int=null

AS

if @ParentId is not null

begin

select

ParentId,

ChildID

from

TBL0410ParentChild

where

ParentId=@ParentId

return 0

end

select

ParentId,

ChildID

from

TBL0410ParentChild

return 0

Example 4-19 Stored procedure: SP0410_InsertChild

CREATE PROCEDURE SP0410_InsertChild

@ChildId int output,

@Field3 nvarchar(50)=null,

@Field4 nvarchar(50)=null

AS

SET NOCOUNT ON

insert TBL0410Child(

Field3,

Field4)

values (

@Field3,

@Field4)

if @@rowcount=0

return 1

set @ChildId=Scope_Identity( )

select @ChildId ChildId

return 0

Example 4-20 Stored procedure: SP0410_InsertParent

CREATE PROCEDURE SP0410_InsertParent

@ParentId int output,

@Field1 nvarchar(50)=null,

@Field2 nvarchar(50)=null

AS

SET NOCOUNT ON

insert TBL0410Parent(

Field1,

Field2)

values (

@Field1,

@Field2)

if @@rowcount=0

return 1

set @ParentId=Scope_Identity( )

select @ParentId ParentId

return 0

Example 4-21 Stored procedure: SP0410_InsertParentChild

CREATE PROCEDURE SP0410_InsertParentChild

@ParentId int,

@ChildId int

AS

SET NOCOUNT ON

insert TBL0410ParentChild(

ParentId,

ChildId)

values (

@ParentId,

@ChildId)

if @@rowcount=0

return 1

return 0

Example 4-22 Stored procedure: SP0410_UpdateChild

CREATE PROCEDURE SP0410_UpdateChild

@ChildId int,

@Field3 nvarchar(50)=null,

@Field4 nvarchar(50)=null

AS

SET NOCOUNT ON

update

TBL0410Child

set

Field3=@Field3,

Field4=@Field4

where

ChildId=@ChildId

if @@rowcount=0

return 1

return 0

Example 4-23 Stored procedure: SP0410_UpdateParent

CREATE PROCEDURE SP0410_UpdateParent

@ParentId int,

@Field1 nvarchar(50)=null,

@Field2 nvarchar(50)=null

AS

SET NOCOUNT ON

update

TBL0410Parent

set

Field1=@Field1,

Field2=@Field2

where

ParentId=@ParentId

if @@rowcount=0

return 1

return 0

The C# code for updating a DataSet with a many-to-one relationship is shown in

Example 4-24

Example 4-24 File: UpdateManyToManyRelationshipForm.cs

// Namespaces, variables, and constants

using System;

using System.Configuration;

using System.Windows.Forms;

using System.Data;

using System.Data.SqlClient;

private DataSet ds;

private SqlDataAdapter daParent, daParentChild, daChild;

private const String PARENTTABLENAME = "TBL0410Parent";

private const String PARENTCHILDTABLENAME = "TBL0410ParentChild"; private const String CHILDTABLENAME = "TBL0410Child";

// Table column name constants for Parent table

private const String PARENTID_FIELD = "ParentId";

private const String FIELD1_FIELD = "Field1";

private const String FIELD2_FIELD = "Field2";

// Table column parameter name constants for Child table

private const String CHILDID_FIELD = "ChildId";

private const String FIELD3_FIELD = "Field3";

private const String FIELD4_FIELD = "Field4";

// Stored procedure name constants

private const String DELETEPARENT_SP = "SP0410_DeleteParent"; private const String GETPARENT_SP = "SP0410_GetParent";

private const String INSERTPARENT_SP = "SP0410_InsertParent";

private const String UPDATEPARENT_SP = "SP0410_UpdateParent"; private const String DELETEPARENTCHILD_SP =

"SP0410_DeleteParentChild";

private const String GETPARENTCHILD_SP = "SP0410_GetParentChild"; private const String INSERTPARENTCHILD_SP =

"SP0410_InsertParentChild";

private const String DELETECHILD_SP = "SP0410_DeleteChild";

private const String GETCHILD_SP = "SP0410_GetChild";

private const String INSERTCHILD_SP = "SP0410_InsertChild";

private const String UPDATECHILD_SP = "SP0410_UpdateChild";

// stored procedure parameter name constants for Parent table

private const String PARENTID_PARM = "@ParentId";

private const String FIELD1_PARM = "@Field1";

private const String FIELD2_PARM = "@Field2";

// Stored procedure parameter name constants for Child table

private const String CHILDID_PARM = "@ChildId";

private const String FIELD3_PARM = "@Field3";

private const String FIELD4_PARM = "@Field4";

//

private void UpdateManyToManyRelationshipForm_Load(object sender,

System.EventArgs e)

{

DataColumnCollection cols;

DataColumn col;

// Build the parent table

DataTable parentTable = new DataTable(PARENTTABLENAME);

cols = parentTable.Columns;

col = cols.Add(PARENTID_FIELD, typeof(Int32));

col.AutoIncrement = true;

col.AutoIncrementSeed = -1;

col.AutoIncrementStep = -1;

cols.Add(FIELD1_FIELD, typeof(String)).MaxLength = 50;

cols.Add(FIELD2_FIELD, typeof(String)).MaxLength = 50;

// Build the ParentChild table

DataTable parentChildTable = new DataTable(PARENTCHILDTABLENAME); cols = parentChildTable.Columns;

cols.Add(PARENTID_FIELD, typeof(Int32)).AllowDBNull = false;

cols.Add(CHILDID_FIELD, typeof(Int32)).AllowDBNull = false;

parentChildTable.PrimaryKey = new DataColumn[]

{cols[PARENTID_FIELD], cols[CHILDID_FIELD]};

// Build the child table

DataTable childTable = new DataTable(CHILDTABLENAME);

cols = childTable.Columns;

col = cols.Add(CHILDID_FIELD, typeof(Int32));

col.AutoIncrement = true;

col.AutoIncrementSeed = -1;

col.AutoIncrementStep = -1;

cols.Add(FIELD3_FIELD, typeof(String)).MaxLength = 50;

cols.Add(FIELD4_FIELD, typeof(String)).MaxLength = 50;

// Add the tables to the DataSet and create the relationship

ds = new DataSet( );

ds.Tables.Add(parentTable);

ds.Tables.Add(parentChildTable);

ds.Tables.Add(childTable);

ds.Relations.Add(new DataRelation("Parent_ParentChild",

parentTable.Columns[PARENTID_FIELD],

parentChildTable.Columns[PARENTID_FIELD], true));

ds.Relations.Add(new DataRelation("Child_ParentChild",

childTable.Columns[CHILDID_FIELD],

parentChildTable.Columns[CHILDID_FIELD], true));

// Create the Parent DataAdapter

daParent = new SqlDataAdapter(GETPARENT_SP,

ConfigurationSettings.AppSettings["Sql_ConnectString"]);

daParent.SelectCommand.CommandType = CommandType.StoredProcedure;

// Build the parent delete command

SqlCommand deleteCommand = new SqlCommand(DELETEPARENT_SP, daParent.SelectCommand.Connection);

deleteCommand.CommandType = CommandType.StoredProcedure;

deleteCommand.Parameters.Add(PARENTID_PARM, SqlDbType.Int, 0, PARENTID_FIELD);

daParent.DeleteCommand = deleteCommand;

// Build the parent insert command

SqlCommand insertCommand = new SqlCommand(INSERTPARENT_SP, daParent.SelectCommand.Connection);

insertCommand.CommandType = CommandType.StoredProcedure;

insertCommand.Parameters.Add(PARENTID_PARM, SqlDbType.Int, 0, PARENTID_FIELD);

insertCommand.Parameters.Add(FIELD1_PARM, SqlDbType.NVarChar, 50, FIELD1_FIELD);

insertCommand.Parameters.Add(FIELD2_PARM, SqlDbType.NVarChar, 50, FIELD2_FIELD);

daParent.InsertCommand = insertCommand;

// Build the parent update command

SqlCommand updateCommand = new SqlCommand(UPDATEPARENT_SP,

daParent.SelectCommand.Connection);

updateCommand.CommandType = CommandType.StoredProcedure;

updateCommand.Parameters.Add(PARENTID_PARM, SqlDbType.Int, 0, PARENTID_FIELD);

updateCommand.Parameters.Add(FIELD1_PARM, SqlDbType.NVarChar, 50, FIELD1_FIELD);

updateCommand.Parameters.Add(FIELD2_PARM, SqlDbType.NVarChar, 50, FIELD2_FIELD);

daParent.UpdateCommand = updateCommand;

// Create the Child DataAdapter

daChild = new SqlDataAdapter(GETCHILD_SP,

ConfigurationSettings.AppSettings["Sql_ConnectString"]);

daChild.SelectCommand.CommandType = CommandType.StoredProcedure;

// Build the child delete command

deleteCommand = new SqlCommand(DELETECHILD_SP,

daChild.SelectCommand.Connection);

deleteCommand.CommandType = CommandType.StoredProcedure;

deleteCommand.Parameters.Add(CHILDID_PARM, SqlDbType.Int, 0,

CHILDID_FIELD);

daChild.DeleteCommand = deleteCommand;

// Build the child insert command

insertCommand = new SqlCommand(INSERTCHILD_SP,

daChild.SelectCommand.Connection);

insertCommand.CommandType = CommandType.StoredProcedure;

insertCommand.Parameters.Add(CHILDID_PARM, SqlDbType.Int, 0,

CHILDID_FIELD);

insertCommand.Parameters.Add(FIELD3_PARM, SqlDbType.NVarChar, 50, FIELD3_FIELD);

insertCommand.Parameters.Add(FIELD4_PARM, SqlDbType.NVarChar, 50, FIELD4_FIELD);

daChild.InsertCommand = insertCommand;

// Build the child update command

updateCommand = new SqlCommand(UPDATECHILD_SP,

daChild.SelectCommand.Connection);

updateCommand.CommandType = CommandType.StoredProcedure;

updateCommand.Parameters.Add(CHILDID_PARM, SqlDbType.Int, 0,

CHILDID_FIELD);

updateCommand.Parameters.Add(FIELD3_PARM, SqlDbType.NVarChar, 50,