Tài liệu Restore a SQL Server Database doc

7.3 Restore a SQL Server Database Sometimes the user needs to restore a database, and again, it is nice if he doesn't have to go to Enterprise Manager to accomplish this task.. This How-

7.3 Restore a SQL Server Database

Sometimes the user needs to restore a database, and again, it is nice if he doesn't have to

go to Enterprise Manager to accomplish this task This How-To explains how to use the Restore object from SQL-DMO to accomplish this task

It's all well and good to be able to back up and verify a SQL Server database, but what about being able to restore the database if necessary? How do you create a dialog box to restore a SQL Server database?

Technique

For this How-To, you will use the Restore object of the SQL-DMO object model You can see the properties and methods that will be used in Table 7.5

Table 7.5 Properties and Methods of the Restore Object Property/Method Description

Action This property allows you to specify what type of backup you want to

take place The choices are found in the SQLDMO.SQLDMO_RESTORE_TYPE namespace and are SQLDMORestore_Database, SQLDMORestore_Files, SQLDMORestore_Log

Database This property allows you to specify the database name to restore to Devices This property shows which device(s) you are restoring from

ReplaceDatabase This property tells whether to replace the database

SQLRestore This method causes the restore to be executed

Using the objects listed in Table 7.5, you will create a form with options for the user to restore his database

Steps

Open and run the VB.NET -Chapter 7 solution From the main Windows Form, click on the command button with the caption How-To 7.3 You will then see the form displayed

in Figure 7.8

Figure 7.8 This form restores a SQL Server database

As with How-To 7.2, a user clicks on the SQL Server for which he wants to display the

databases He can then choose the database and backup device From there, the user can

click the Restore button to restore the database

1 Create a Windows Form Then place the controls shown in Figure 7.8, with the

following properties set as in Table 7.6

Table 7.6 Label, ListBox, DataGrid, and Command Button Controls

Property Settings

Command Button Name btnBackup

Command Button Name btnClose

2 On the form, add the code in Listing 7.14 to the Load event This will look

familiar from the first How-To For an examination of the LoadSQLServers

routine, check out step 4 in How-To 7.1

Listing 7.14 frmHowTo7_3.vb: Calling the Routine That Loads Available SQL Servers into a List Box

Private Sub frmHowTo7_3_Load(ByVal sender As System.Object, _

ByVal e As System.EventArgs) Handles MyBase.Load

' Load up the SQL Servers

LoadSQLServers(Me.lstSQLServers)

End Sub

3 On the lstSQLServers list box, add the code in Listing 7.15 to the

SelectedIndexChanged event This routine calls both GetSQLDatabases, described

in step 6 of How-To 7.1, and GetBackupDevices, described in step 4 of How-To 7.2

Listing 7.15 frmHowTo7_3.vb: Populating the lstDatabases and

lstBackupDevices List Boxes

Private Sub lstSQLServers_SelectedIndexChanged(ByVal sender As

System.Object,

ByVal e As System.EventArgs) _

Handles lstSQLServers.SelectedIndexChanged

GetSQLDatabases(Me.lstSQLServers.SelectedItem, Me.lstDatabases)

GetBackupDevices(Me.lstSQLServers.SelectedItem, Me.lstBackupDevices)

End Sub

4 On the btnRestore button, add the code in Listing 7.16 to the Click event After logging into the server, the Restore object is created and its properties are set from the form The SQLRestore method is invoked and the connection is closed

Listing 7.16 frmHowTo7_3.vb: Performing the Backup

Private Sub btnRestore_Click(ByVal sender As System.Object, _

ByVal e As System.EventArgs) Handles btnRestore.Click

' Create a connection to the server

Dim osvr As New SQLDMO.SQLServer()

osvr.LoginSecure = True

osvr.Connect(Me.lstSQLServers.SelectedItem)

' Create the restore object, set the properties from the form,

' and execute the restore

Dim oRestore As New SQLDMO.Restore()

With oRestore

Action =

SQLDMO.SQLDMO_RESTORE_TYPE.SQLDMORestore_Database

Database = Me.lstDatabases.SelectedItem

Devices = "[" & Me.lstBackupDevices.SelectedItem & "]"

ReplaceDatabase = Me.chkReplaceDB.Checked

SQLRestore(osvr)

End With

' Disconnect and clean up

osvr.DisConnect()

osvr = Nothing

oRestore = Nothing

MessageBox.Show("Database Restored", "Task Completed", _

MessageBoxButtons.OK)

End Sub

5 Add the code in Listing 7.17 to the Click event of btnClose

Listing 7.17 frmHowTo7_3.vb: Performing the Backup

Private Sub btnClose_Click(ByVal sender As System.Object, _

ByVal e As System.EventArgs) Handles btnClose.Click

Me.Close()

End Sub

How It Works

The Restore object is the counter object to the Backup object, allowing you to restore databases that have been backed up As with the Backup object, you can either specify the properties yourself or let the user choose them on the form

Comments

Again, you need to be careful which options you let the user specify and which you specify yourself This is a utility that you might want to secure; only let an administrator have access to it so that users don't accidentally overwrite a good database with an old one

As with the backup, you could enhance this utility by allowing the user to specify a file to restore from instead of a backup device