Is2215 lecture8 relational_databases

RELATIONAL DATABASEDEALING WITH MORE THAN ONE TABLE

Set up the objectsDim objConnection As New

OleDb.OleDbConnection( _ "Provider=Microsoft.Ace.OLEDB.12.0;Data

Source =C:\DataBase.accdb")Dim objTableDA As New _

OleDb.OleDbDataAdapter("Select * from Table", _ objConnection)

Dim objTableCB As New _ OleDb.OleDbCommandBuilder(objTableDA)

Dim objDataSet As New DataSet()

1. Setting up Objects

2. Filling the DataSet

objDataSet.Clear()

objTableDA.FillSchema(objDataSet, _ SchemaType.Source, “Table")

objTableDA.Fill(objDataSet, “Table")

3. Displaying Data on Form

Dim objRow As DataRow objRow = _ objDataSet.Tables(“Table").

Rows.Find _ (Insert Code for Primary Key Here)

lblField1Text = objRow.Item(“Field1") txtField2.Text = objRow.Item(“Field2") txtField3.Text = objRow.Item(“Field3") End Sub

Row 0Row 1Row 2Row 3

Column 0

4.Storing Details

Public Sub StoreDetails() Dim objRow As DataRow objRow = _

objDataSet.Tables(“Table").Rows.Find(PrimaryKey)

objRow.Item(“Field1") = txtField1.Text objRow.Item(“Field2") = txtField2.Text End Sub

5. Update Changes to DataSet In the previous slide we updated our

database but…

objTableDA.Update(objDataSet, “Table”)

6.Add a New Row to DataSet

Dim objRow As DataRowobjRow =

objDataSet.Tables(“Table”).NewRowobjRow.Item(“Field1”) = InputBox(“Field1?”)objRow.Item(“Field2”) = InputBox(“Field2?”)objRow.Item(“Field3”) = InputBox(“Field3?”)objDataSet.Tables(“Table”).Rows.Add(objRo

w)objTableDA.Update(objDataSet, “Table”)

7. Deleting a Row

Dim objRow As DataRow objRow =

objDataSet.Tables(“Tables").Rows.Find(PrimaryKey)

objRow.Delete() objTableDA.Update(objDataSet, “Table")

Retrieve()

1.Setting up Objects

Dim objConnection As New OleDb.OleDbConnection( _

"Provider=Microsoft.ACE.OLEDB.12.0;Data Source _ =surgery.accdb")

Dim objOwnerDA As New OleDb.OleDbDataAdapter("Select * from Owners", _ objConnection)

Dim objOwnerCB As New OleDb.OleDbCommandBuilder(objOwnerDA)

Dim objDS As New DataSet()

2.Fill the Data Set

objDS.Clear()

objOwnerDA.FillSchema(objDS, _ SchemaType.Source, "Owners")

objOwnerDA.Fill(objDataSet, "Owners")

Row 0Row 1Row 2Row 3

Row 0Row 1Row 2Row 3

‘objDS.Tables("Owners").Rows.Count = 4‘For i = 0 to 4 would cause a problem‘There is no row 4!

3.Populate ComboBox cboOwners.Items.Clear()

Dim i As Integer, strCurrentID As String

For i = 0 To objDS.Tables("Owners").Rows.Count - 1

strCurrentID = _

objDS.Tables("Owners").Rows(i).Item("OwnerID")

cboOwners.Items.Add(strCurrentID)

Next

cboOwners.SelectedIndex = 0

4.Display a Record

Public Sub FillOwnersDetails() Dim objRow As DataRow objRow = _ objDS.Tables("Owners").Rows.Find _ (cboOwners.SelectedItem.ToString)

lblOwnerID.Text = _ objRow.Item("OwnerID")

txtName.Text = objRow.Item("Name") txtAddress.Text = objRow.Item("Address") End Sub

5.Storing Details

Public Sub StoreOwnerDetails()

Dim objRow As DataRowIf lblOwnerID.Text = "" Then Exit SubobjRow = _ objDS.Tables("Owners").Rows.Find _ (lblOwnerID.Text)

objRow.Item("Name") = txtName.Text objRow.Item("Address") = _ txtAddress.Text

End Sub

6.ImplementProcedures

Call the Fill Owner Details behind the Combo Box

7.Persisting Changes

Code to be placed behind the save button

If the user has made changes to a field we want to store the changes to the dataset and then persist those changes to the DB

1.Call the StoreOwnerDetails()2.objOwnerDA.Update(objDS, “Owners”)

8.Add Row to our DataSetDim objRow As DataRowobjRow = objDS.Tables(“Owners”).NewRowobjRow.Item(“OwnerID”) = InputBox(“Owner

ID?”)objRow.Item(“Name”) = InputBox(“Name?”)objRow.Item(“Address”) =

InputBox(“Address?”)objDS.Tables(“Owners”).Rows.Add(objRow)StoreOwnerDetails()objOwnerDA.Update(objDS, “Owners”)

Remember to loop through records again !

9.Deleting a Row

Dim objRow As DataRow objRow = _ objDS.Tables("Owners")._ Rows.Find(cboOwners.SelectedItem.ToString)

objRow.Delete() objOwnerDA.Update(objDS, "Owners")Retrieve()

10.Creating Relationships

We have created two tables owners and pets.

What if we want to use both tables on our form?

Pull data from both tables into our dataset

Then set up an OwnerID relationship between the two.

11.Set up more Objects

Dim objPetDA as New _ OleDbDataAdapter(“Select * from Pets”,_ , objConnection)Dim objPetCB As New _OleDbCommandBuilder(objPetDA)

lstPets

Filling in Pet Details

Add the following code to your Retrieve button code or Retrieve Method

It should go in after you have filled the dataset with Owners data

objPetDA.FillSchema(objDataSet, _ SchemaType.Source, "Pets")objPetDA.Fill(objDS, "Pets")'Setup our RelationshipobjDS.Relations.Clear()objDS.Relations.Add("Owners2Pets", _objDS.Tables("Owners").Columns("OwnerID"), _objDS.Tables("Pets").Columns("OwnerID"))

FillPetDetails()

Public Sub FillPetDetails()

Dim objOwner As DataRow, objPet As _ DataRowDim strPetEntry As StringlstPets.Items.Clear()

objOwner = objDS.Tables(“Owners”)._ Rows.Find(cboOwners.SelectedItem.ToString)

Loop through records

For Each objPet in objOwner.GetChildRows(“Owners2Pets”)

strPetEntry = objItem(“PetID”) & “, “ ” & _

objPet.Item(“PetName”) & “, “ & objPet.Item(“Type”)

lstPets.Items.Add(strPetEntry)

Next

End Sub

Finishing Touches

To end of your retrieve records code add the following line:

FillPetDetails() Add the following code to the

SelectedIndexChanged event of our combo box:

FillPetDetails()