1. INT213
Updating the Database

2. Contents
Cursors
Locking
Updating databases

3. Cursors
So far, we have stepped through a Recordset in the forward direction one record at a time
This technique uses the simplest cursor, the forward-Looking-Only cursor
A cursor is simply a pointer that indicates your current location in the Recordset

4. Cursors A cursor points to a specific row
BOF
A cursor points to a specific row
Different types of cursors can
Move forward
Move backward
Move by several rows
A cursor cannot
Move before the first record (Beginning Of File)
Move after the last record (End Of File)
Row 1
cursor
Row 2
Row n
EOF

5. Cursor Types Cursor Constant Value Description Forward only
adOpenForwardOnly
Moves forward only, one by one. Fastest performing cursortype, and also the most limited. The forward-only cursor does not support the RecordCount property, and does not support the MovePrevious methods of the recordset object.
Static
adOpenStatic 3
The result is not updated when changes are made to the database
Keyset
adOpenKeyset 1
Not applicable to this course
Dynamic
adOpenDynamic 2
This reevaluates the query each time a new row is requested. Thus, new rows added are detected.

6. Scrollable Cursors All cursors, except forward-only, are scrollable
This means they can move in more than just the forward direction
Scrollable cursors support the methods
MoveFirst – move to the first record
MoveLast – move to the last record
MoveNext – move to the next record
MovePrevious – move to the previous record
Move n – move n records forward or back

7. Selecting a Cursor RecordSet.Open
The cursor is selected via one of the parameters used when opening the RecordSet
RecordSet.Open
source, (sql statement, stored procedure or table name)
connection, (connection string or connection object)
cursorType, (How to move through RecordSet)
LockType, (Whether to read or write to a table)
commandType (describes the source)

8. Selecting a Cursor To create a static cursor
set RS = Server.CreateObject ("ADODB.Recordset")
query = "SELECT * FROM Person ORDER BY lastName"
RS.Open query, objConn, adOpenStatic
To output a RecordSet in reverse
rs.MoveLast
Do While Not RS.BOF
Response.Write RS("firstName") & " " & RS("lastName") & "<br>"
RS.MovePrevious
Loop

9. Adovbs.inc
So far we have defined the constants for the cursor types ourselves
These are actually in a file called adovbs.inc
You can include this in your scripts
<!--#include virtual=“adovbs.inc”-->
<!--#include file=“adovbs.inc”-->

10. Counting Records
How do you determine the number of records in a RecordSet?
Have a loop Move through the RecordSet and count them
Use the RecordCount property of a scrollable cursor
Response.Write "The number of names is " & RS.RecordCount & "<br>"

11. Locking
When two people try to update a record at the same time, confusion and errors result
To avoid this problem, VBScript can be configured to lock the records
This means that one person locks the record and updates it
The other person cannot read or update the record until the first person releases their lock

12. Lock Types Lock Constant Description Read-only adLockReadOnly
Records are read-only and cannot be modified or added. Default lock type.
Pessimistic
adLockPessimistic
Records are locked as soon as editing begins.
Optimistic
adLockOptimistic
Locks row only when update is called. Used when having multiple users making changes to the same records is not a major concern.
Batch optimistic
adLockBatchOptimistic
Outside course scope

13. Syntax for Opening Record Sets
Open a Scrollable, updatable Recordset with parameters
sql = “Select * from students”
Rs.open sql, conn, adOpenStatic, adLockOptimistic, adCmdText
Open a RecordSet after setting the properties
Set rs = Server.CreateObject("ADODB.RecordSet")
rs.LockType = adLockOptimistic
rs.CursorType = adOpenStatic
rs.Open sql, conn
* adCmdText – indicates that the source holds command text, such as an
SQL command

14. Adding Records If you call RS.AddNew
It will create a new, blank record and make it the current record
You can then assign values to the fields
Finally, call
RS.Update to write the changes to the DB

15. Adding Records RS.AddNew RS(“firstName”) = “Fred”
RS(“lastName”) = “Flintstone”
RS.Update

16. Updating Records To update an existing record
Get the record from the database
Modify the field(s)
Call Update or CancelUpdate
RS(“firstName”) = “Frederick”
RS.Update

17. Deleting Records You can delete an existing record by
Find the record you want to delete (sql query)
Call RS.Delete
RS.MoveFirst
RS.Delete