1. VBA Data Access Object

2. Data Access Objects DAO With DAO we can: –Run queries –Update values in database tables –Create structure of databases Tables, relationship, etc. Mainly used for Access databases

4. Workspace Example Dim wrkJet As Workspace Dim dbsNorthwind As Database Dim dbsSalesDB As Database Dim rs1 As Recordset Dim rs2 As Recordset Set wrkJet = CreateWorkspace("", "admin", "", dbUseJet) Set dbsNorthwind = wrkJet.OpenDatabase("c:\Northwind.mdb") Set dbsSalesDB = wrkJet.OpenDatabase("c:\SalesDB.mdb") Set rs1 = dbsSalesDB.OpenRecordset("customer") MsgBox (dbsSalesDB.Recordsets.Count) Set rs2 = dbsNorthwind.OpenRecordset("customers") MsgBox (rs1.Fields(0)) MsgBox (rs2.Fields(0))

5. DAO Programming Retrieving data by running a select query –Creating recordset Iterating through the records in a recordset, one record at a time. Running an action query –Update –Delete –Insert

6. A Simplified DAO Model Database –RecordSet Fields –Relation

7. Open a Database Using Workspace object’s OpenDatabase method: –Dim db As Database –Set db=OpenDatabase(“path to database”) Using Application object’s CurrentDB method: –Dim db As Database –Set db = CurrentDb

8. Database Object’s Methods Execute:Executes an SQL statement. –dbsSalesDB.Execute "update customer set rating='C' where cid='c02'" OpenRecordSet: –Creates a new RecordSet object and appends it to the Recordsets collection.

9. RecordSet Type Table:Connected to a table directly –Editable, and fast because table can be indexed –Single table Dynaset: Representing a set of references to the result of a query. The query can retrieve data from multiple tables. –Updatable Snapshot: Return a copy of data. –Not updatable Forward-only: A snapshot that can only move forward.

10. Creating a RecordSet Dim db As Database Dim rs As RecordSet Set db = OpenDatabase(“path to database”) Set rs = db.OpenRecordSet(“tableName”) Or Set rs= db.OpenRecordSet(“sql statement”)

11. RecordSet Options dbOpenTable dbOpenDynaset dbOpenSnapshot dbOpenForwardOnly Example: Set rs = db.OpenRecordset("customer", dbOpenForwardOnly)

12. Reading a Field in a RecordSet Text0 = rs.Fields("cid") Text2 = rs.Fields("cname")

13. Navigate RecordSet Rs.MoveNext –MoveLast –MovePrevious –MoveFirst Rs.EOF RS.BOF

14. BOF and EOF in a Record Set BOF Record # 1 Record # 2 Record #3 EOF

15. Loop through a Recordset Do While Not Recordset.EOF ‘Perform action on data Recordset.MoveNext Loop

16. Navigate RecordSet with a Loop Set db = OpenDatabase("c:\salesdb.mdb") Set rs = db.OpenRecordset("customer") Do While Not rs.EOF List6.AddItem rs.Fields("cid") rs.MoveNext Loop Note: Listbox RowSource Type property must set to Value List

17. Unbound Form Dim db As Database Dim rs As Recordset Private Sub Command4_Click() rs.MoveNext If Not rs.EOF Then Me.Text0 = rs.Fields("cid") Me.Text2 = rs.Fields("cname") Else MsgBox ("End of File") End If End Sub Private Sub Command5_Click() rs.MovePrevious If Not rs.BOF Then Me.Text0 = rs.Fields("cid") Me.Text2 = rs.Fields("cname") Else MsgBox ("BOF") End If End Sub Private Sub Form_Load() Set db = CurrentDb Set rs = db.OpenRecordset("select cid, cname from customer") Me.Text0 = rs.Fields("cid") Me.Text2 = rs.Fields("cname") End Sub

18. Other RecordSet Properties Object Browser