ActiveX Data Object (ADO)ActiveX Data Object (ADO)in JavaScriptin JavaScript

J.L.Wang, Yen-Cheng Chen

Dept. of Infomation Management

Ming-Chuan University

Jan. 1999

OutlinesOutlines

Overview Object model of ADO ADO techniques

ADO OverviewADO Overview

ADO allow us to write code in a scripting language that can interact with a database

The missing link between the web page and almost any kind of stored data

ADO Data InterfaceADO Data Interface

To interface with database through ODBC Use it with any data source for which an O

DBC driver is available ODBC

OOpen DDataBBase CConnectivity

Data ProviderData Provider

Active Server PageActive Database Component

ADOODBC Driver Data Provider

Interface

DataSource

ADO Object ModelADO Object Model Connection Object

Establish an active connection that allows us to gain access to data stored in a database

Command Object Obtain records, excute SQL queries, or mani

pulate the data Recordset Object

Access the data that is returned from executing an SQL query

ADO Object HierarchyADO Object Hierarchy

Collection

Object

Property collection Error collection

Connection Object

Field collection Property collection

Parameter collection Property collection

Recordset Object

Command object

Connection ObjectConnection Object Connection

Represent the physical link between applications and the remote database server

All communications between Recordset or Commands and the back-end database is negotiated through the connection

Transaction Make the interaction with the database bulletproof A series of changes can be grouped together to look l

ike a single, all-or-nothing (atomic) change

Connection Object: Connection Object: Basic FlowBasic Flow

Create an instance of the Connection object global.asa: Session_onStart or Application_onStart

Open a connection: data source name (DSN) Execute commands:SQL command Close the connection

Release the object resource

Connection Object: Basic CommandsConnection Object: Basic Commands

ObjCon=Server.CreateObject(“ADODB.Conneciton”) Create an instance of the Connection object

ObjCon.Open(“DSN”):Open a connection ObjCon.Execute(“SQL COMMAND”)

Execute an execution, the result can be stored in a recordset

ObjCon.Close(): Close the connection ObjCon.BeginTrans(): Begins a new transaction ObjCon.CommitTrans(): Saves any changes and ends the tr

ansaction, May also start a new transaction ObjCon.RollbackTrans(): Cancel any changes and ends the

transaction. May also start a new transaction

<%@language=JScript%><%conn=Server.CreateObject("ADODB.Connection");conn.Open("ExampleAdoDSN");rs=conn.Execute("select * from Books");Response.Write("<center><h2>Books</h2>");Response.Write("<table border=1><tr>");cnt=rs.Fields.Count;for (i=0;i<cnt;i++) { Response.Write("<th>"+rs(i).Name+"</th>");}Response.Write("</tr>\n");while (! rs.EOF) { Response.Write("<tr>"); for (i=0;i<cnt;i++) { Response.Write("<td>"+rs(i)+"</td>"); } Response.Write("</tr>\n"); rs.MoveNext();}Response.Write("</table>\n");Response.Write("</center>");conn.Close();conn=null; %>

Connection ScopeConnection Scope

global.asa Session_onStart

function Session_onStart() {ObjCon=Server.CreateObject(“ADODB.Conneciton”)

...

} Application_onStart

function Application_onStart() {ObjCon=Server.CreateObject(“ADODB.Conneciton”)

...

}

Connection TransactionConnection Transaction Perform a series of updates on a data source

Get the system to store up all the changes, and then commit them in one go Before actually commit the change, the chnages can be rolling back

ObjCon=Server.CreateObject(“ADODB.Conneciton”)ObjCon.Open("DSN")ObjCon.BeginTrans()ObjCon.Execute(“SQL COMMAND”)If (Conditions) { ObjCon.CommitTrans // Serve any changes }Else { ObjConn.RollbackTrans // Cancel any changes }}ObjCon.Close()

Command ObjectCommand Object Provide methods and properties to manipulate individual commands Methods

CreateParameter: Create a new Parameter object that can be appended to the Parameters collections

Execute: Execute the SQL statement or stored procedure Property

ActiveConnection: Active one connection to be used by command object (DSN)

CommandText: Text of a command to be execute CommandTimeout: No. of second for finishing a command CommandType:

adCmdText(1), adCmdTable(2), adCmdStoreProc(3),adCmdUnknown(3) Prepared: Whether to create a prepare statement before exec

ution (a command could be executed for multiple times)

Command Object: Basic CommandsCommand Object: Basic Commands

Create an instance of the Command object ObjCmd=Server.CreateObject(“ADOBE.Command”)

Create an active connection ObjCmd.ActiveConnection = “DSN” ObjCmd.ActiveConnection = someConnectionObject

Execution a query ObjCmd.CommandText = “SQL Command” ObjCmd.CommandType = 1 // SQL query ObjCmd.Prepared = true // Compile the stateme

nt ObjCmd.Execute()

Release the resource used ObjCmd.ActiveConnection = null

<%@language=JScript%><%cmd=Server.CreateObject("ADODB.Command");cmd=Server.CreateObject("ADODB.Command");cmd.ActiveConnection="ExampleAdoDSN";cmd.ActiveConnection="ExampleAdoDSN";cmd.CommandText="select * from Books";cmd.CommandText="select * from Books";rs=cmd.Execute();rs=cmd.Execute();cnt=rs.Fields.Count;Response.Write("<center><h2>Books</h2>");Response.Write("<table border=1><tr>");for (i=0;i<cnt;i++) { Response.Write("<th>"+rs(i).Name+"</th>");}Response.Write("</tr>\n");while (! rs.EOF) { Response.Write("<tr>"); for (i=0;i<cnt;i++) { Response.Write("<td>"+rs(i)+"</td>"); } Response.Write("</tr>\n"); rs.MoveNext();}Response.Write("</table>\n");Response.Write("</center>");cmd=null;%>

function GenerateTable(rs, tableTitle)GenerateTable(rs, tableTitle) { cnt=rs.Fields.Count; Response.Write("<h2>tableTitle</h2>"); Response.Write("<table border=1><tr>"); for (i=0;i<cnt;i++) { Response.Write("<th>"+rs(i).Name+"</th>"); } Response.Write("</tr>\n"); while (! rs.EOF) { Response.Write("<tr>"); for (i=0;i<cnt;i++) { Response.Write("<td>"+rs(i)+"</td>"); } Response.Write("</tr>\n"); rs.MoveNext(); } Response.Write("</table>\n");}

<%@language=JScript%><%

function GenerateTable(rs, tableTitle) {. . . }

cmd=Server.CreateObject("ADODB.Command");cmd=Server.CreateObject("ADODB.Command");cmd.ActiveConnection="ExampleAdoDSN";cmd.ActiveConnection="ExampleAdoDSN";cmd.CommandText="select * from Books";cmd.CommandText="select * from Books";rs=cmd.Execute();rs=cmd.Execute();GenerateTable(rs, "Books");GenerateTable(rs, "Books");

%>%>

Recordset ObjectRecordset Object

Assign the query results to a Recordset object Like a table in memory Can create recorsets containing the data returned

from that query Can even create a recordset directly, without

having to open a connection or execute a command first

Recordset FundamentalsRecordset Fundamentals

Open the recordsetSet rs=Server.CreateObject(“ADODB.Recordset”)

rs.Open(“select * from Books”, “DSN=ExampleAdoDSN;”)

Access the data fieldfirstname = rs(“fieldname”)

firstname = rs.Fields(“fieldname”)

n = rs.Fields.Count // get the number of fields

Navigate the recordswhile (! rs.EOF) {

// do something with the data

rs.MoveNext()

}

<%@language=JScript%><% rs=Server.CreateObject("ADODB.Recordset");conn=Server.CreateObject("ADODB.Connection");conn.Open("ExampleAdoDSN");rs.Open("select * from Books", conn);cnt=rs.Fields.Count;Response.Write("<center><h2>Books</h2>");Response.Write("<table border=1><tr>");for (i=0;i<cnt;i++) { Response.Write("<th>"+rs(i).Name+"</th>");}Response.Write("</tr>\n");while (! rs.EOF) { Response.Write("<tr>"); for (i=0;i<cnt;i++) { Response.Write("<td>"+rs(i)+"</td>"); } Response.Write("</tr>\n"); rs.MoveNext();}Response.Write("</table>\n");Response.Write("</center>");...%>

Recordset: PropertiesRecordset: Properties AbsolutePage: Page of current position AbsolutePosition: The original position of the current record ActiveConnection: Active connection object BOF: Before of first record ( True or False ) Bookmark: Return/set a bookmark CacheSize: Number of records cached CursorLocation: Server, client, or client batch CursorType: Forwarde, static, dynamic, keyset EditMode: The editing status ( backward compatible with DAO) EOF: End of file ( True or False ) Filter: Hide types of records LockType: Record locking for edits or updates MaxRecords: Maximum records retrieved PageSize: Number of pages total RecordCount: Number of total records Source: Source command Status: Status of the last action

CursorTypeCursorType Dynamic: adOpenDynamic

Fully updateable recordset All actions made by other users while the recordset is open are visibleAll types of movement ( up and down )

Keyset: adOpenKeysetUpdateable recordsetIt prevents access to records that other users add after it was createdAll types of movement

Static: adOpenStaticStatic non-updateable recordset ( retrieve data )Changes made by other users while the recordset is open aren’t visibleAll types of movement

Forward-only: adOpenForwardOnly (default)Static non-updateable recordset Only Scroll forward through the records (MoveNext, GetRows)

actions: additions, changes & deletion

Recordset: MethodRecordset: Method AddNew: Create a new record in an updateable recordset CancelBatch: Cancels a pending batch update CancelUpdate: Cancel any changes made to the current or a new record Clone: Create identical Recordset Close: Close an open recordset Delete: Delete the current record GetRows: Get multiple records Move: Move the position of the current record MoveFirst, MoveLast, MoveNext, MovePrevious NextRecordset: Move to the next set in multi-set query Open: Establish a connection and execute the query Requery: Refresh the data ( re-execute the original query ) Resync: Synchronize data with server Supports: Determine supported features Update: Save any changes made to the current record UpdateBatch: Write all pending batch updates to disk

Recordset: Create Recordset DirectlyRecordset: Create Recordset Directly Create a recordset

ObjRS = Server.CreateObject(“ADODB.Recordset”) Fill the new recordset with values from the data source

ObjRS.Open(Source,ActiveConnection,CursorType,LockType,Options) Source: A Command object, SQL statement, table name or stored procedure ActiveConnection: Data Source Name CursorTYpe: adOpenForwardOnly (default) LockType: adLockReadOnly (default) Options: The type of query or table represented by Source

adCmdUnknows(0): Unknown(default) adCmdText(1): SQL statement adCmdText(2): Table name for creating a recordset adCmdStoredProc(3): A stored procedure

Recordset: MovingRecordset: Moving ObjRS.Move(n): Moving

-n : move backward n records

n: forward ( interger ) ObjRS.AbsolutePosition

the current record number

Return value-1 (adPosUnknown: No current record (be deleted)

-2 (adPosBOF): Before the first record

-3 (adPosEOF): After the last record

Recordset: ConnectionRecordset: Connection

ObjCon=Server.CreateObject(“ADODB.Conneciton”)ObjCon.Open(“DSN”)ObjRS = ObjCon.Execute (“SQL COMMAND”)….

Recordset: Recordset: CommandCommand

ObjCmd = Server.CreateObject(“ADOBE.Command”)

ObjCmd.ActiveConnection = “DSN”

ObjCmd.CommandText = “SELECT * FROM JobCon”

ObjCmd.CommandType = adCmdText

ObjRS = ObjCmd.Execute()

…

Recordset:Table/CommandRecordset:Table/Command

ObjCmd = Server.CreateObject(“ADOBE.Command”)ObjCmd.ActiveConnection = “DSN”ObjRS = ObjCmd.Execute (“TableName”,,adCmdTable)...ObjRS.Close() …

ObjCmd = Server.CreateObject(“ADOBE.Command”)ObjCmd.ActiveConnection = “DSN”ObjCmd.CommandText = “TableName”ObjCmd.CommandType = adCmdTable

ObjRS = ObjCmd.Execute()…ObjRS .Close()

…

Recordset:IterationRecordset:Iteration

ObjCon = Server.CreateObject(“ADODB.Connection”)

ObjCon.Open(“DSN”)

ObjRS = ObjCon.Execute(“TableName”, , adCmdTable)

ObjRS.MoveFirst()

While (! ObjRS.EOF) {

…

ObjRS.MoveNext()

}