ASP page display
If you have used the electronic bulletin board on many websites, then you should know that the electronic bulletin program is to increase the page read speed.
Generally don't list all the posts in one page, but divide them into multi-page display, each page
Show a number of posts, such as 20. Do you want to know how to implement pagination display? Please see
This article!
So how do you want to display the database's query result paging? In fact, there are many ways.
But there are two main types:
First, read all the records in the database in accordance with the query conditions in the database, read in the Recordset.
Store in memory, then several special support panesses provided by the ADO Recordset object
Property: PageSize (Page size), PageCount (number of pages) and
AbsolutePage (absolute page) to manage paging processing.
Second, according to the customer's instruction, each time respectively, from the record of the query condition, the specified number
The record number is read and displayed.
The main difference between the two is that the former is one-time to read all records in memory and then according to the instructions.
To make judgment analysis to achieve the effect of paging display, the latter is to make judgments according to the instructions
Read the specified number of records that meet the query criteria, so that the features of the paging display are directly reached.
We can feel obvious that when the number of records in the database reaches tens of thousands or more, the first
The implementation efficiency of the method will be significantly lower than the second method, because when each customer query page is
Store all eligible records in server memory, and then processed by paging, if
At the same time, there are more than 100 customer online queries, then the execution efficiency of the ASP application will be large.
influences. However, when the number of records on the server and the number of online people are not a lot,
The two are different in operation, and the first method is generally used in this time because the first
Method's ASP program preparations relative second method should be simple and clear.
Here, the author takes advantage of our common ASP BBS program to analyze how
Implement the paging display in the BBS program, due to the database of BBS programs we generally used
The number of records and the number of people visited will not be too much, so the following program instance is the previous introduction.
The first paging display method.
Paging display when using ADO access database, is actually a record of Recordset
Operation. So we must first learn about the properties and methods of the REORDSET object:
BOF attribute: The current indicator refers to the first pen of Recordset.
EOF attribute: The current indicator refers to the last pen of Recordset.
MOVE method: Move the indicator to a record in the Recordset.
AbsolutePage Properties: Which page is located in the location of the current record?
AbsolutePosition Attribute: The location of the current indicator in the Recordset.
PageCount Properties: Displays the Recordset object that includes how much "page".
PageSize Attribute: Displays the number of records displayed in each page of the Recordset object.
RecordCount Properties: Displays the total number of recordset object records.
Let's let us know more about these important properties and methods.
First, Bof and EOF attribute
Usually we write code in the ASP program to verify BOF and EOF properties, thus
The location of the Recordset, which is currently pointed to by the indicator, can learn about the BOF and EOF properties.
Does a RecordSet object contain a record or know if the mobile record line has exceeded
The range of Recordset objects.
Such as: <% if not rs.eof the ...%> <% if not (rs.bof and %e)%>
If the location of the current record is before the first line of Recordset objects, BOF
The property returns true, and then false returns FALSE.
If the current recorded position is after a recording record last line record,
The EOF property returns true, and then returns false.
BOF and EOF are false: indicates that the indicator is located in the Recordset.
BOF is true: The current indicator refers to the first record of the Recordset.
EOF is True: The current indicator refers to the last record of the Recordset.
Bof and EOF are True: There is no record in the Recordset.
Second, MOVE method
You can use the MOVE method to move the indicator to a record in the Recordset, the syntax is as follows:
Rs.Move NumRecords, Start
The "RS" here is an object variable, indicating that one wants to move when the current record position
Recordset object; "NUMRECORDS" is a positive and negative number, setting the current record location
Movement; "start" is an optional item that specifies the label that records the starting.
All Recordset objects support Move methods if NumRecords parameters
Big than zero, the current record position moves in the end of the end; if it is less than zero, the current record location
Move in the direction of the beginning; if an empty RecordSet object calls the MOVE method,
Generate an error.
MoveFirst method: Move the current recording location to the first record.
MoveLAST method: Move the current record position to the last record.
MoveNext method: Move the current recording location to the next record.
MovePRevious method: Move the current record position to the previous record.
Move [N] Method: Move indicator to the nth record, N is calculated from 0.
Third, absolutePage properties
AbsolutePage Properties Setting the location of the current record is where the page number is located;
Use the PageSize property to divide the RecordSet object into logical pages, records for each page
The number is PageSize (except for the last page may have less than the number of records of the PageSize). Here
Be careful not to support this attribute, so be careful when using it.
As with the AbsolutePosition property, the AbsolutePage property is starting with 1
If the current record of Recordset is currently recorded, AbsolutePage is 1. can
Set the AbsolutePage property to move to the first row record location of a specified page.
Fourth, AbsolutePosition Attribute
If you need to determine the location of the current indicator in the Recordset, you can use
AbsolutePosition attribute.
The value of the absolutePosition attribute is the current indicator relative to the first position, from 1
Mandarin, the first AbsolutePosition is 1.
Note that when accessing RecordSet, it is not possible to ensure that RecordSet is the same.
The order appears.
To enable AbsolutePosition, you must first set to use the user end.
The CURSOR (pointer), the ASP code is as follows:
rs2.cursorlocation = 3 5, PageCount properties
Using the PageCount property, determine the data of the Recordset object including how much "page".
The "page" here is the collection of data records, the size is equal to the setting of the PageSize property, even
The number of records is less than the value of PageSize, and the last page is also a page of PageCount.
It is important to note that all data providers support this attribute.
6. PageSize property
The PageSize property is how to make a pagination display when the ADO access database is determined.
You can decide how much records make up a logically "one page". Set and build a size of a page,
This allows the first record that allows the AbsolutePage property to move to other logical pages.
The PageSize property is set at any time.
Seven, RecordCount properties
This is also a very common and important attribute, we often use the RecordCount property to find
A RecordSet object includes how many records. Such as:
<% TOTLE = rs.Recordcount%>
After understanding the above properties and methods of the Recordset object, let's consider it.
How to use them to reach our pagination display. First, we can be the PageSize property.
Set a value to specify the number of rows that make up from the record group; then pass
RecordCount property to determine the total number of records; re-use the total number of records to be available in PageSize
To the total number of pages displayed; Finally, access to the specified page via the AbsolutePage property.
It seems that it is not complicated. Let's take a look at how the program is implemented?
We establish such a simple BBS application, which have the following five in their databases, respectively.
Field: "ID", automatic number of each post; "Subject", the topic of each post;
"Name", the name of the user; "email", the user's email address;
"Postdate", the time of the addition. The DSN of the database is "BBS". We will show the post
All steps for paging are placed in a process called "showlist ()", which is convenient to call.
The procedure is as follows:
'---- BBS Display Posts Page ----
<% Sub showlist ()%>
<%
PGSZ = 20 'setting switch, specify the number of posts shown in each page, default is 20 sheets
Set conn = server.createObject ("adoDb.connection")
SET RS = Server.createObject ("AdoDb.Recordset")
SQL = "SELECT * from message Order by id"
'Query all posts and follow the ID of the post
Conn.open "BBS"
RS.Open SQL, CONN, 1, 1
IF = 0 THEN
Response.write "
Else
Rs.pagesize = cint (pgsz) Set the value of the PageSize property
Total = int (rs.recordcount / pgsz * -1) * - 1 'calculates the total number of displayed pages
Pageno = Request ("Pageno")
IF Pageno = "" ""
Pageno = 1
Else
Pageno = PAGENO 1
Pageno = PAGENO-1
END IF
Scrolaction = Request ("scroll")
IF scrollAction = "Previous" THEN
Pageno = PAGENO-1
END IF
If scrollAction = "Next page" THEN
Pageno = PAGENO 1
END IF
IF Pageno <1 THEN
Pageno = 1
END IF
n = 1
Rs.absolutePage = Pageno
Response.write "
Position = rs.pagesize * Pageno
Pagebegin = position-rs.pageSize 1
IF position Pagend = position Else Pagend = rs.Recordcount END IF Response.write " database query results: " Response.write "(a total of" & RS.RecordCount & "strips meet the requirements, Show "& Pagebegin &" - "& Pagend &") " Response.write "
