Download Recordset Object(Cont.)

Active Data Objects
By CSJue
Microsoft Database Tech.
• DAO (Data Access Objects)
– 由C++寫成, 架構在JET database engine上, 可以直接
存取和控制database。
• ODBC(Open Database Connectivity)
– 以C寫成的API, 為MS定的一個Open standard 。
• RDO(Remote Data Objects)
– 由C++寫成, 架構在ODBC上, 其特點為充分支援網
路。
Microsoft Database Tech.(cont.)
Client
Server
Server
RDO
IIS
Server
ODBC
• OLE DB
– 由C++寫成, 可處理多種資料(如ODBC, 試算表, EMail, text, file…..), 並支援網路。
Microsoft Database Tech.(cont.)
• ADO(Active Data Objects)
– 由C寫成, 目的在使OLE DB用起來方便, 它用
ActiveX技術把OLE DB包起來。
Client/Data Consumer
DAO
RDO
ODBC
Relational data
ADO
ODBC OLE
Provider DB
Text
Data
Streams
The ADO Object Model
ActiveConnection
The ADO Object Model(Cont.)
• Connection object: Create a connection to a
data provider.
• Recordset object: Create a set of records from
a query.
• Command object: Execute SQL strings, stored
procedures, or action queries
• Fields Collection:Recordset objects contain a
collection of Field Objects that gives you access to
column metadata
The ADO Object Model(Cont.)
• Parameters Collection: Contains all of the
parameters associated with the Command
object.
• Errors Collection:Connection objects
contain an Errors collection.
• Properties Collection:Connection, Command,
Recordset, and Field objects all include a
Properties collection.
Connection object
• 主要在建立和維護Command object, 使用
它來管理Recordset object.
• 建立Connection Object
Set objConn = Server.CreateObject(“ADODB.Connection”)
ObjConn.Open =”DSN=myDSN;UID=master;PWD=slave”
Set objRst = objConn.Execute(CommandText, RecordsAffected,
Options)
• Connection pooling - 60 sec(default)
• Connection timeout - 15 sec(default)
Connection object (cont.)
• Transactions
ObjConn.BeginTrans();
…………………..
If(ObjConn.Errors.Count=0)Then
ObjConn.CommitTrans
Else
ObjConn.RollbackTrans
End If
• Execute method
– 直接建立recordset object, 但只能得到一個唯
讀, 向前的游標
Connection object (cont.)
– Set objRst = objConn.Execute(CommandText,
RecordsAffected, Options);
數值
Command Text 的型式
1
2
Options
adCmdText
adCmdTable
4
adCmdStoredProc
Stored procedure 或
querydef
8
adCmdUnknown
未知的
原文
Table 名稱
Connection object (cont.)
• IsolationLevel
–解決Dirty Reads, Nonrepeatable Reads,
Phantom Records等同時性控制的問題
– adXactUnspecified(-1), adXactChaos(16),
adXactBrowse (256), adXactReadUncommited
(256), adXactCursorStability (4096),
adXactReadCommitted (4096),
adXactIsolated(1048576), adXactSerializable
(1048576)
Command object
• 主要在達成query
• 建立Command object
way1: Set objCmd = Server.CreateObject(“ADODB.Command”)
Set objCmd.ActiveConnection = objConn
ObjCmd.CommandText=”qryPhoneMessagesFor”
way2:objCmd.ActiveConnection = “dsn=intranet ; database= intranet;
uid=sa;pwd=..;” Or
objCmd.ActiveConnection = ”DRIVER={Microsoft Access
Driver(*.mdb)}; DBQ=c:\data\…..\XXX.mdb”
Command object(cont.)
• Execute method
– pCommand->Execute(RecordsAffcted,
Parameters, Options)
• CreateParameter & Parameters Collection
Recordset Object
• 完成資料庫管理, 查詢的工作
• 建立Recordset object
– 設 定 好 A c t i v e Co n n ec t i o n , C u r s o r Ty p e ,
LockType, Source properties後, 呼叫Open
method, 或直接把它們傳給Open method-pRecordset->Open(source, activeconnection,
cursortype, LockType, options)
Recordset Object(Cont.)
– CursorType:
Recordset Object(Cont.)
– Options:
Recordset Object(Cont.)
• Bookmark(用Rst.supports(adBookmark)測
有無支援)
• Page
– 相關properties:AbsolutePage, PageSize,
PageCount…
Recordset Object(Cont.)
• Filter
– way1:使用判斷標準常數~adFilterNone(0),
adFilterPendingRecords (1), adFilterAffectedRecords
(2), adFilterFetchedRecords(3)
– 使用比較字串來過濾:
• objRst.Filter = “for = ‘mpc’ AND on = ‘Date’ ”
• GetRows: Fetches a block of rows into an
array.
Recordset Object(Cont.)
• Adding Data
Rst.Addnew
Rst(“field1”) = value1
Rst(“field2”) = value2
………….
Rst.Update (EX. Addcust1.html)
• Updating data
Rst(“field1”) = value1
……
rst.Update(EX. Update.asp)
Using ADO Objects in VC++
• Using #import
#import “C:\ProgramFiles\Common Files\System\ADO\MSADO10.DLL”
no_namespace rename(“EOF”, “ADOEOF”)
• Initializing COM
CoInitialize(NULL);
CoUninitialize();
• Creating ADO objects
_ConnectionPtr pConn;
hr = pConn.CreateInstance( “ADODB.Connection”);
• The ADO License Key
Reference
• Http://www.microsoft/accessdev/articles/mo
ves202.htm ~ ADO Programming(ASP)
• http://www.microsoft.com/data/ado/sams/ch
08.htm
• http://www.microsoft.com/data/ado
• Visual C++5 by David Bennett, part V
• 深入Active Server Pages ~ ch15, 16, 17