IS 4506 Database Connectivity

 Overview Two and Three-Tier C/S Architecture ASP Database Connection ODBC - Connection to DBMS Overview of transaction processing

Client /Server Architecture Database Server PCs Middleware

Web Client/Server Architecture Client Web Browser HTTP Server INTERNETINTRANET

Multi-Tier Client/Server Architecture Database Server Client Web Browser HTTP Server INTERNETINTRANET

ODBC Errors a) A user tries to connect to a database via your company’s web site and receives the error "ODBC…" Login failure. What is the possible cause? The user has insufficient permission to access the database. b) A user tries to connect to a database via your company’s web site and receives the error "ODBC…" General network error. What is the possible cause? Due to heavy use, the database was recently moved to another server.

ODBC Errors c) A user tries to connect to a database via your company’s web site and receives the error "ODBC…" MS OLE ODBC provider for ODBC driver error MS ODBC driver manager. Data source name not found and no default driver specified. What is the possible cause? Data source name is configured incorrectly. d) A user tries to connect to a database via your company’s web site and receives the error "ODBC…" Unable to find resources. What is the possible cause? ODBC driver not configured.

ASP Code <% Set OBJdbConnection = Server.CreateObject("ADODB.Connection") OBJdbConnection.Open "is4506","", "” strSQL = "INSERT INTO Students (FName,LName, ) VALUES ('" & Request.Form("first") & "', '" & Request.Form("last") & "','" & Request.Form(" ") & "')" OBJdbConnection.Execute(strSQL) OBJdbConnection.Close %>

 Database Connection - Input Set OBJdbConnection = Server.CreateObject("ADODB.Connection") OBJdbConnection.Open "is4506","", "" strSQL = "INSERT INTO Students(fname,lname) VALUES ('" & Request.Form("fname") & "', '" & Request.Form("lname") & "')" OBJdbConnection.Execute(strSQL) OBJdbConnection.Close

 Database Connection - Update Set OBJdbConnection = Server.CreateObject("ADODB.Connection") OBJdbConnection.Open "is4506","", "" ifname = Request.Form("fname") 'example of using a variable in the SQL expression strSQL = "UPDATE Students SET fname = ('" & ifname & "'), lname = ('" & Request.Form("lname") & "') WHERE ID = (" & Request.Form("ID") & ")" OBJdbConnection.Execute(strSQL) OBJdbConnection.Close

 Database Connection - Delete Set OBJdbConnection = Server.CreateObject("ADODB.Connection") OBJdbConnection.Open "is4506","", "" 'Note that the single apostrophe is missing from the ID expression when using numbers vice strings. strSQL = "DELETE FROM Students WHERE ID = (" & Request.Form("ID") & ")" OBJdbConnection.Execute(strSQL) OBJdbConnection.Close

 Overview of Transaction Processing Transaction A unit of work that succeeds or fails as a whole Method for coordinating a series of changes made to a resource or sets of resources ACID Properties Atomicity Consistency Isolation Durability

ACID Properties Atomicity - Either all changes happen or none happen. Consistency - Actions taken as a group do not violate any integrity. Isolation - For actions that execute concurrently, one is either executed before or after the other, but not both. Durability - Changes survive failures of process, network, operating system, and others.

Three-Tier Architecture Presentation Business/Data components Data access

Components of a Transaction Network Receiver Queue Connections Security Thread Pool Service Logic Synchronization Shared Data Context DB Manager Configuration Client

The Bank Example Four Components Account Modifies an account Move Money Debit, credit, or transfer Receipt Get unique # Update receipt Allocation 100 receipt #s Client Transaction Move Money Account Update Receipt

MSDE MSDE is a stripped down version of SQL Server that is included with Access 2000 and Access The Access 2000 version is named Microsoft Data Engine. It is a stripped down version of SQL Server 7. It can be installed directly from the Office 2000 CD from the following location: SQL\x86\SETUP\SETUPSQL.EXE The Access 2002 version is named Microsoft Desktop Engine. It is a stripped down version of SQL Server It can also be installed directly from the CD from the following location: MSDE\SETUP.EXE Both servers are fully functional SQL Servers but they do not include a user interface like Enterprise Manager.