ADO Recordsets

Recordset Objects

• Similar to Tables and Queries: data

• Using VBA/VBScript you…– Open a recordset, – Locate a record– Update or add a record– Close

Controls on Forms I: Recordsets

• The usual job of forms: showing data from tables/queries

• With recordsets, you must use VBA/VBScript to show data in controls

• You fill listboxes, textboxes, etc• The form doesn't fill them for you• This is not "bound forms"

Controls on Forms II: Recordsets

• Another job of forms: taking data from controls into tables/queries

• With recordsets, you must use VBA/VBScript to take form data from the controls and save it

• The listboxes, textboxes, etc are the source of tabled data

• But, the form doesn't update the table for you• This is not "bound forms"

Bound forms vs. Recordsets

• Use standard forms for input and output• Use recordset programming to…

– Read data from tables/queries– Fill controls on forms with this data– Read data in controls on forms– Update the tables/queries with user changes to the

form data

But, do not use recordset programming instead of binding forms to tables/queries. Use it to augment forms.

Opening with Recordset Cursors

The cursor element controls:• record navigation• updatability of data• visibility of changes by other users• speed of application

Types of Cursors• Static

• Dynamic

• KeySet

• ForwardOnly

Static Cursor

• A static copy of a set of records that you can use to find data or generate reports

• Additions, changes, or deletions by other users are not visible

• Bookmarks are supported• MovePrevious is available• RecordCount property is available• Supports batch updates (SQL Server)

Opening Static Tables

' our textbook opens static-cursor recordsets like thisDim cnn As adodb.ConnectionDim rst As New adodb.Recordset Set cnn = CurrentProject.Connectionrst.Open "tblPeople",cnn, adOpenStatic

' … records are processed as needed ' and then the table is closed safely

rst.Close Set rst = Nothing

Dynamic Cursor• Additions, changes, and deletions by other users

are visible• all types of movement through the recordset are

allowed• Not a fast cursor• MovePrevious is available• Bookmarks not supported• RecordCount property is not available• Does not support batch updates

Opening Dynamic Tables

' our textbook opens table-recordsets like thisDim cnn As adodb.Connection

Dim rst As New adodb.Recordset

Set cnn = CurrentProject.Connection

rst.Open "tblPeople",cnn,adOpenDynamic, , adCmdTable

' … records are processed as needed

' and then the table is closed safely rst.Close

Set rst = Nothing

Opening Dynamic SQL

' SQL recordsets can restrict and order the records as follows

Dim strSQL As StringstrSQL = "SELECT * From tblEmployee " & _ "WHERE HireDate < #01/01/90# " & _ "ORDER BY HireDate" Dim cnn As adodb.ConnectionDim rst As New adodb.Recordset Set cnn = CurrentProject.Connectionrst.Open strSQL, cnn, adOpenDynamic,,adCmdText ' … process as needed …rst.CloseSet rst = Nothing

KeySet Cursor

• Like a dynamic cursor, but faster

• Bookmarks are supported, unlike dynamic

• Data changes by other users are visible

• Deleted recs by other users are inaccessible

• Can't see records that other users add:– Until you refresh the cursor with rst.Resync

• Supports batch updates (SQL Server)

Static/Dynamic/Keyset Cursor Recordsets (finding numbers)

• Locate records, not just one record• Should open with SQL for speedier finds

rst.MoveFirstRst.Find "pkPeopleID=" & cboNavigationIf rst.EOF or rst.BOF = True then MsgBox "Failed to find "Endif

Static/Dynamic/Keyset Cursor

Recordsets (finding dates)

• Locate records, not just one record• Should open with SQL for speedier findsdteHire=#01/03/01#strFind="HireDate=" & "#" & dteHire & "#"rst.MoveLastrst.Find strFind ,, adSearchBackward If rst.BOF = True then MsgBox "Failed to find "Endif

Static/Dynamic/Keyset Cursor

Recordsets (finding strings)

• Locate records, not just one record• Should open with SQL for speedier findsstrName="Poynor"strCriteria="LastName=" & "'" & strName & "'"rst.MoveFirstrst.Find strCriteria ,, adSearchForward If rst.EOF = True then MsgBox "Failed to find "Endif

Static/Dynamic/Keyset Cursor

Recordsets (seeking strings)

rst.Index = "LastNameIndex" ' this index MUST be hard coded in the table!! rst.Open "tblPeople", cnn, adOpenStatic, adLockOptimistic, adCmdTableDirect strWhich = "first: " ' strWhich is used below strName = InputBox("Enter a last name") rst.Seek strName, adSeekFirstEQ

Do Until strName <> rst!LastName ' loop works bc rst is ordered by last name Debug.Print "Sought " & strWhich & rst!FirstName & " " & rst!LastName rst.MoveNext strWhich = "next: " Loop

Locate records fast based on a table index

ForwardOnly Cursor

• This is the default Cursor• You only scroll forward through records• Improves performance when you make only one

pass through a recordset• Bookmarks not supported• Update, AddNew are not available• MovePrevious, Find are not available• RecordCount property is not available• Does not support batch updates

Moving in Recordset (BOF)

rst.MovePrevious

If rst.BOF = True Then….

' true if you tried to go before the first record

rst.MoveNext

If rst.EOF = True Then….

' true if you tried to go after the last record

Moving in Recordset (EOF)

' here is how to store a recordset into an array

Dim varArray() as Variant

rst.MoveFirst

varArray = rst.GetRows

rst.Close

' how many records and fields were stored? (Chap. 8)

intRecordCount = UBound(varArray, 2) + 1

intFieldCount = UBound(varArray, 1) + 1

'stored as varArray(Fields, Records)

Arrays created from Recordsets

rst!FirstName = "Carrie"

rst(1) = "Carrie"

rst("FirstName") = "Carrie"

rst.Fields.Item(1).Value = "Carrie"

rst!LastName = "Ohn"

Recordsets Syntax for Fields

rst.Open "tblPeople",CurrentProject.Connection,adOpenStatic,adLockOptimistic ' necessary to write

rst.Find "pkPeopleID=" & 8If not rst.EOF then rst!Salary = 62000

rst.Update 'save changes

rst.CancelUpdate 'OR cancel the update

Editing Recordsets

rst.Open "tblPeople",CurrentProject.Connection,adOpenStatic,adLockOptimistic ' necessary to write

rst.AddNew ' add a blank record ' optional to add values to fields rst!Salary = 52000

rst!Sex = "F"rst!FirstName="Sammin"

rst!MiddleName="Janet"rst!LastName="Evening"

rst.Update 'save changes rst.CancelUpdate 'OR cancel the new record

Adding to Recordsets(two-step process)

rst.Delete ' that's all folks

Deleting from Recordsets

Dim varBookmark As Variant

varBookmark = rst.Bookmark ' remember position

rst.MoveFirst ' start at first position

Do While Not rst.EOF

' calculate something you need

rst.MoveNext ' move to next position

Loop

rst.Bookmark = varBookmark ' restore position

' this will throw an error for dynamic and forward cursors. To prevent the error message (but live with no bookmarks) use this logic:

If rs.Supports(adBookmark) Then…

Keeping track of record position in recordsets