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(fù)制到數(shù)組中。
語法
array = recordset.GetRows( Rows, Start, Fields )
返回值
返回二維數(shù)組。
參數(shù)
Rows 可選,長整型表達(dá)式,指定要檢索記錄數(shù)。默認(rèn)值為 adGetRowsRest (-1)。
Start 可選,字符串或長整型,計(jì)算得到在 GetRows 操作開始處的記錄的書簽。也可使用下列 BookmarkEnum 值。
常量 說明
AdBookmarkCurrent 從當(dāng)前記錄開始。
AdBookmarkFirst 從首記錄開始。
AdBookmarkLast 從尾記錄開始。
Fields 可選,變體型,代表單個(gè)字段名、順序位置、字段名數(shù)組或順序位置號。ADO 僅返回這些字段中的數(shù)據(jù)。
說明
使用 GetRows 方法可將記錄從 Recordset 復(fù)制到二維數(shù)組中。第一個(gè)下標(biāo)標(biāo)識字段,第二個(gè)則標(biāo)識記錄號。當(dāng) GetRows 方法返回?cái)?shù)據(jù)時(shí)數(shù)組變量將自動(dòng)調(diào)整到正確大小。
如果不指定 Rows 參數(shù)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(shù)。
如果 Recordset 對象支持書簽,則可以通過傳送該記錄的 Bookmark 屬性值,來指定 GetRows 方法將從哪個(gè)記錄開始檢索數(shù)據(jù)。
如要限制 GetRows 調(diào)用返回的字段,則可以在 Fields 參數(shù)中傳送單個(gè)字段名/編號或者字段名/編號數(shù)組。
在調(diào)用 GetRows 后,下一個(gè)未讀取的記錄成為當(dāng)前記錄,或者如果沒有更多的記錄,則 EOF 屬性設(shè)置為 True。
GetString方法
查詢數(shù)據(jù)庫顯示表格時(shí),我們常用Do While()...Loop 或者是For...Next循環(huán)來顯示表格,這樣當(dāng)我們要查詢大量數(shù)據(jù)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)。
語法
Str=objRecordset.GetString(format,n,coldel,rowdel,nullexpr)
參數(shù)說明:
objRecordset:已打開的記錄集對象;
format:可選,一般取默認(rèn)值(默認(rèn)值為2)
n:可選,顯示記錄的數(shù)量,默認(rèn)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(shù)用于填充空字段!
有了GetString方法,我們就可以僅用一個(gè)Response.Write來顯示所有的輸出了,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(zhí)行了相應(yīng)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(jié)果里生成HTML表格,我們只需關(guān)心GetString的5個(gè)參數(shù)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(dāng)前記錄為空時(shí)應(yīng)生成的HTML代碼)。
<TABLE Border=1> <TR><TD> <% = Response.Write rs.GetString( , , "</TD><TD>", "</TD></TR><TR>", ) %> </TABLE>
這樣寫的HTML結(jié)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,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>" %>
你用過嗎。。。
看到了嗎?可以直接從查詢中返回結(jié)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(bǔ)充一下
ASP里使用GetString來循環(huán)讀取數(shù)據(jù)的具體方法及實(shí)例
在ASP里,我們要循環(huán)讀取數(shù)據(jù)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有效率,并且會(huì)影響網(wǎng)頁程序打開的速度。
當(dāng)我們只是從數(shù)據(jù)庫里讀取并顯示數(shù)據(jù)的時(shí)候,我們可以用GetString來加速讀取數(shù)據(jù),并顯示到網(wǎng)頁上,使用GetString會(huì)大大增加我們從數(shù)據(jù)庫讀取數(shù)據(jù)的效率。
本文站長就和大家來說說ASP里使用GetString的方法,先來看GetString的具體語法結(jié)構(gòu):
Str=objRecordset.GetString(format,n,coldel,rowdel,nullexpr)
'參數(shù):
objRecordset :為我們打開的rs記錄集
format:可選,一般取默認(rèn)值(默認(rèn)值為2)
n:可選,顯示記錄的數(shù)量,默認(rèn)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(shù)用于填充空字段!
下面站長給大家提供一個(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>") %>
以上就是asp中記錄集對象的getrows和getstring用法分析的詳細(xì)內(nèi)容,更多關(guān)于記錄集 getrows getstring的資料請關(guān)注腳本之家其它相關(guān)文章!
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