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

dataBut, 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 this

Dim cnn As adodb.ConnectionDim rst As New adodb.Recordset Set cnn = CurrentProject.Connectionrst.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 followsDim 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