Shulou(Shulou.com)06/02 Report--

This article introduces the relevant knowledge of "what is an ADO Access database cursor". In the operation of actual cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

Adopenforwardonly: forward cursor only, default. It is the same as a static cursor except that it can only scroll forward in the record. Use it to improve performance when you only need to move one-way through the recordset. (as the name implies, this cursor can only move forward. However, due to the limited functionality of this cursor, it is very effective to use it for system resources. )

Adopenkeyset: keyset cursors. Although records deleted by other users cannot be accessed from your recordset, keyset cursors are similar to dynamic cursors except that you cannot view records added by other users. Data changed by other users can still be seen in the ADO Access database. The keyset cursor allows you to see changes made by other users since it was created, while you cannot see records that other users have added or deleted. )

Adopendynamic: dynamic cursors. You can see the additions, changes, and deletions made by other users. All types of movements are allowed in the recordset, except for bookmark operations that are not supported by the provider. (this type of cursor is powerful and consumes the most system resources. ADO Access database cursors can see all the changes to their collection of saved records. Users using dynamic cursors can see edits, additions, and deletions made by other users. If the data provider allows this type of cursor, it supports this visibility by retrieving data from the data source at regular intervals. There is no doubt that this will require a lot of resources. )

Adopenstatic: static cursors. A static copy of a collection of records that can be used to find data or generate reports. In addition, additions, changes, or deletions to other users are not visible. Static cursors are just a snapshot of the data. That is, it cannot see the changes that other users have made to recordset since it was created. With this kind of cursor, you can sail forward and backward. Because of its simple function, the demand for resources is smaller than dynamic! )

It is important to note that once you open recordset, you cannot change the cursortype property. However, ADO Access database if you first close recordset, change the cursortype property, and then reopen recordset, you can still effectively change the type of cursor!

In any database application that can be modified by multiple users at the same time, you have to deal with the possibility of multiple users operating on the same record at the same time. When this happens, the integrity of the data is threatened because a user may unconsciously overwrite others' changes when saving their own changes. At that time, you will feel as if you have done nothing. To deal with this situation. Ado allows you to determine the type of concurrent event control when updating recordset objects, and how a user locks records when he edits. This is determined by the locktype attribute. This property has four values:

Adlockreadonly: default, read-only. The ADO Access database cannot change the data. (this is the default value for recodset, and if you set the locking method to this value, you will not be able to update recordset. )

Adlockpessimistic: conservative record locking (item by item). The provider performs the necessary actions to ensure successful editing of the record, usually by locking the record of the data source immediately when editing. (if set to this type of lock, the record is locked and can only be accessed by users who edit between the beginning of the editing and the submission of the record update to the data provider!)

This is the end of the content of "what is the ADO Access database cursor?" Thank you for reading. If you want to know more about the industry, you can follow the website, the editor will output more high-quality practical articles for you!

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.