asp中記錄集對象的getrows和getstring用法分析

GetRows 方法

將 Recordset 對象的多個(gè)記錄復制到數組中。
語(yǔ)法

array = recordset.GetRows( Rows, Start, Fields )

返回值
返回二維數組。
參數
Rows 可選，長(cháng)整型表達式，指定要檢索記錄數。默認值為 adGetRowsRest (-1)。
Start 可選，字符串或長(cháng)整型，計算得到在 GetRows 操作開(kāi)始處的記錄的書(shū)簽。也可使用下列 BookmarkEnum 值。

常量　　　　　　　　　　　說(shuō)明
AdBookmarkCurrent 　　從當前記錄開(kāi)始。
AdBookmarkFirst 　　　　從首記錄開(kāi)始。
AdBookmarkLast　　　　 從尾記錄開(kāi)始。

Fields 可選，變體型，代表單個(gè)字段名、順序位置、字段名數組或順序位置號。ADO 僅返回這些字段中的數據。
說(shuō)明
使用 GetRows 方法可將記錄從 Recordset 復制到二維數組中。第一個(gè)下標標識字段，第二個(gè)則標識記錄號。當 GetRows 方法返回數據時(shí)數組變量將自動(dòng)調整到正確大小。
如果不指定 Rows 參數的值，GetRows 方法將自動(dòng)檢索 Recordset 對象中的所有記錄。如果請求的記錄比可用記錄多，則 GetRows 僅返回可用記錄數。
如果 Recordset 對象支持書(shū)簽，則可以通過(guò)傳送該記錄的 Bookmark 屬性值，來(lái)指定 GetRows 方法將從哪個(gè)記錄開(kāi)始檢索數據。
如要限制 GetRows 調用返回的字段，則可以在 Fields 參數中傳送單個(gè)字段名/編號或者字段名/編號數組。
在調用 GetRows 后，下一個(gè)未讀取的記錄成為當前記錄，或者如果沒(méi)有更多的記錄，則 EOF 屬性設置為 True。

GetString方法

查詢(xún)數據庫顯示表格時(shí),我們常用Do While()...Loop 或者是For...Next循環(huán)來(lái)顯示表格,這樣當我們要查詢(xún)大量數據時(shí),勢必會(huì )比較慢。這時(shí)，我們就可以用記錄集對象提供的GetString()方法(ADO必須升級到2.0)。
語(yǔ)法

Str=objRecordset.GetString(format,n,coldel,rowdel,nullexpr)

參數說(shuō)明:
objRecordset:已打開(kāi)的記錄集對象;
format:可選,一般取默認值(默認值為2)
n:可選,顯示記錄的數量，默認值為全部顯示
coldel:可選,列界定符
rowdel:可選,行界定符
nullexpr:可選,該參數用于填充空字段!
有了GetString方法,我們就可以?xún)H用一個(gè)Response.Write來(lái)顯示所有的輸出了，它就象是能判斷Recordset是否為EOF的DO ... LOOP循環(huán)。
用這個(gè)方法，可以自動(dòng)的循環(huán)輸出字符串,就不用再去while或for循環(huán)了,只要建立了RS對象，并且執行了相應操作，不管那是返回一條或者多條記錄，甚至是空記錄，getstring照樣工作。
要從Recordset的結果里生成HTML表格，我們只需關(guān)心GetString的5個(gè)參數中的3個(gè)：coldel(分隔記錄集的列的HTML代碼)，rowdel(分隔記錄集的行的HTML代碼)，和nullexpr(當前記錄為空時(shí)應生成的HTML代碼)。

<TABLE Border=1> 
<TR><TD> 
<% = Response.Write rs.GetString( , , "</TD><TD>", "</TD></TR><TR>", ) %> 
</TABLE> 

這樣寫(xiě)的HTML結果如下：

<TABLE Border=1> 
<TR> 
<TD>row1, field1 value</TD> 
<TD>row1, field2 value</TD> 
</TR> 
<TR> 
<TD>row2, field1 value</TD> 
<TD>row2, field2 value</TD> 
</TR> 
</TABLE> 

這里有個(gè)BUG了，再看看生成下拉選單：

<% 
Set RS = conn.Execute("Select theValue,theText FROM selectOptionsTable orDER BY theText") 
optSuffix = "</OPTION>" & vbNewLine 
valPrefix = "<OPTION Value='" 
valSuffix = "'>" 
opts = RS.GetString( , , valSuffix, optSuffix & valPrefix, "--error--" ) 
' Next line is the key to it! 
opts = Left( opts, Len(opts)-Len(valPrefix) ) 

Response.Write "<Select ...>" & vbNewLine 
Response.Write valPrefix & opts 
Response.Write "</Select>" 
%> 

如果想建立一個(gè)正確的表格的話(huà)，解決那個(gè)BUG，只要這樣做就可以了：

<% 
Set RS = conn.Execute("Select * FROM table") 
tdSuffix = "</TD>" & vbNewLine & "<TD> 
trPrefix = "<TR>" & vbNewLine & "<TD>" 
trSuffix = "</TD>" & vbNewLine & "</TR>" & vbNewLine & "<TR>" & vbNewLine 
opts = RS.GetString( , , tdSuffix, trSuffix & trPrefix, "--error--" ) 
' Next line is the key to it! 
opts = Left( opts, Len(opts)-Len(trPrefix) ) 
Response.Write "<TABLE Border=1 CellPadding=5>" & vbNewLine 
Response.Write trPrefix & opts 
Response.Write "</TABLE>" & vbNewLine 
%>

再介紹一個(gè)完全不同的辦法：

<% 
SQL = "Select '<OPTION Value=''',value,'''>',text,'</OPTION>' FROM table orDER BY text" 
Set RS = conn.Execute(SQL) 
Response.Write "<Select>" & vbNewLine & RS.GetString(,,"",vbNewLine) & "</Select>" 
%> 

你用過(guò)嗎。。。

看到了嗎？可以直接從查詢(xún)中返回結果。
再進(jìn)一步，您可以這樣做：

<% 
SQL = "Select '<OPTION Value=''' & value & '''>' & text & '</OPTION>' FROM table orDER BY text" 
Set RS = conn.Execute(SQL) 
Response.Write "<Select>" & vbNewLine & RS.GetString(,,"",vbNewLine) & "</Select>" 
%> 

下面是一份完整的示例：

Script Output:
711855 Wednesday 23 3/23/2005 1:33:37 AM
711856 Wednesday 23 3/23/2005 1:23:00 AM
711857 Wednesday 23 3/23/2005 1:26:34 AM
711858 Wednesday 23 3/23/2005 1:33:53 AM
711859 Wednesday 23 3/23/2005 1:30:36 AM

ASP完整代碼如下：

<% 
' Selected constants from adovbs.inc: 
Const adClipString = 2 

' Declare our variables... always good practice! 
Dim cnnGetString ' ADO connection 
Dim rstGetString ' ADO recordset 
Dim strDBPath ' Path to our Access DB (*.mdb) file 
Dim strDBData ' String that we dump all the data into 
Dim strDBDataTable ' String that we dump all the data into 
' only this time we build a table 
' MapPath to our mdb file's physical path. 
strDBPath = Server.MapPath("db_scratch.mdb") 

' Create a Connection using OLE DB 
Set cnnGetString = Server.CreateObject("ADODB.Connection") 

' This line is for the Access sample database: 
'cnnGetString.Open "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" & strDBPath & ";" 
' We're actually using SQL Server so we use this line instead. 
' Comment this line out and uncomment the Access one above to 
' play with the script on your own server. 
cnnGetString.Open "Provider=SQLOLEDB;Data Source=10.2.1.214;" _ 
& "Initial Catalog=samples;User Id=samples;Password=password;" _ 
& "Connect Timeout=15;Network Library=dbmssocn;" 

' Execute a simple query using the connection object. 
' Store the resulting recordset in our variable. 
Set rstGetString = cnnGetString.Execute("Select * FROM scratch") 

' Now this is where it gets interesting... Normally we'd do 
' a loop of some sort until we ran into the last record in 
' in the recordset. This time we're going to get all the data 
' in one fell swoop and dump it into a string so we can 
' disconnect from the DB as quickly as possible. 
strDBData = rstGetString.GetString() 

' Since I'm doing this twice for illustration... I reposition 
' at the beginning of the RS before the second call. 
rstGetString.MoveFirst 

' This time I ask for everything back in HTML table format: 
strDBDataTable = rstGetString.GetString(adClipString, -1, _ 
&"</td><td>", "</td></tr>" & vbCrLf & "<tr><td>", " ") 

' Because of my insatiable desire for neat HTML, I actually 
' truncate the string next. You see, GetString only has 
' a parameter for what goes between rows and not a seperate 
' one for what to place after the last row. Because of the 
' way HTML tables are built, this leaves us with an extra 
' <tr><td> after the last record. GetString places the 
' whole delimiter at the end since it doesn't have anything 
' else to place there and in many situations this works fine. 
' With HTML it's a little bit weird. Most developers simply 
' close the row and move on, but I couldn't bring myself to' 
leave the extra row... especially since it would have a 
' different number of cells then all the others. 
' What can I say... these things tend to bother me. ;) 
strDBDataTable = Left(strDBDataTable, Len(strDBDataTable) - Len("<tr><td>")) 

' Some notes about .GetString: 
' The Method actually takes up to 5 optional arguments: 
' 1. StringFormat - The format in which to return the 
' recordset text. adClipString is the only 
' valid value. 
' 2. NumRows - The number of rows to return. Defaults 
' to -1 indicating all rows. 
' 3. ColumnDelimiter - The text to place in between the columns. 
' Defaults to a tab character 
' 4. RowDelimiter - The text to place in between the rows 
' Defaults to a carriage return 
' 5. NullExpr - Expression to use if a NULL value is 
' returned. Defaults to an empty string. 
' Close our recordset and connection and dispose of the objects. 
' Notice that I'm able to do this before we even worry about 
' displaying any of the data! 
rstGetString.Close 
Set rstGetString = Nothing 
cnnGetString.Close 
Set cnnGetString = Nothing 

' Display the table of the data. I really don't need to do 
' any formatting since the GetString call did most everything 
' for us in terms of building the table text. 
Response.Write "<table border=""1"">" & vbCrLf 
Response.Write "<tr><td>" 
Response.Write strDBDataTable 
Response.Write "</table>" & vbCrLf 
' FYI: Here's the output format you get if you cann GetString 
' without any parameters: 
Response.Write vbCrLf & "<p>Here's the unformatted version:</p>" & vbCrLf 
Response.Write "<pre>" & vbCrLf 
Response.Write strDBDataResponse.Write "</pre>" & vbCrLf 

' That's all folks! 
%> 

下面給大家補充一下

ASP里使用GetString來(lái)循環(huán)讀取數據的具體方法及實(shí)例

在A(yíng)SP里，我們要循環(huán)讀取數據時(shí)，我們通常用的是 while ... wend   或者 do while() .. loop，但這種方法非常的沒(méi)有效率，并且會(huì )影響網(wǎng)頁(yè)程序打開(kāi)的速度。

當我們只是從數據庫里讀取并顯示數據的時(shí)候，我們可以用GetString來(lái)加速讀取數據，并顯示到網(wǎng)頁(yè)上，使用GetString會(huì )大大增加我們從數據庫讀取數據的效率。

本文站長(cháng)就和大家來(lái)說(shuō)說(shuō)ASP里使用GetString的方法，先來(lái)看GetString的具體語(yǔ)法結構：

Str=objRecordset.GetString(format,n,coldel,rowdel,nullexpr)
'參數：
objRecordset ：為我們打開(kāi)的rs記錄集
format:可選,一般取默認值(默認值為2)
n:可選,顯示記錄的數量，默認值為全部顯示
coldel:可選,列界定符
rowdel:可選,行界定符
nullexpr:可選,該參數用于填充空字段!

下面站長(cháng)給大家提供一個(gè)完整的實(shí)例：

<%
set conn = server.CreateObject("adodb.connection")
conn.open "Driver={Microsoft Access Driver (*.mdb)};DBQ=" & server.MapPath("study.mdb")
set rs = server.createobject("adodb.recordset") 
sql = "sel ect * from users"
rs.open sql,conn,1,1 
str=rs.GetString(,,"</td><td>","</td></tr><tr><td>","該字段為空！")
Response.Write("<table border=1><tr><td>"&str&"</td></tr></table>")
%>

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