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CIS 451: ASP.NET & Databases

CIS 451: ASP.NET & Databases. Dr. Ralph D. Westfall February, 2009. What Is a Database?. "shared collection of logically related data" "designed to meet needs of multiple users" McFadden & Hofer, 1994. Database Advantages. less redundant than separate application files

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CIS 451: ASP.NET & Databases

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  1. CIS 451: ASP.NET & Databases Dr. Ralph D. Westfall February, 2009

  2. What Is a Database? • "shared collection of logically related data" • "designed to meet needs of multiple users" • McFadden & Hofer, 1994

  3. Database Advantages • less redundant than separate application files • consistency of data • integration of data • data sharing • easier application development • scalability e.g., Oracle product line

  4. Databases Advantages - 2 • better security, privacy, integrity controls • standardization e.g., field names • data accessibility and responsiveness • data independence • reduced program maintenance • e.g., centralized validation

  5. Database Advantages - 3 • more efficient technology than most "third generation" application programs • powerful code to access items, search and sort • data storage optimization (disk, memory) • efficient updating: add, change, delete

  6. Databases - Disadvantages • use more resources than file-based systems • hardware, software • require specialized personnel • potential data access conflicts • operations vs. data mining • potential organizational conflicts • incompatibilities between database systems

  7. Universal Data Access • ODBC: open database connectivity • standard API for accessing relational databases • API = application programming interface • "drivers" for Access, dBase, DB2, Excel, text, etc. • Microsoft is a leading ODBC backer and ships its own version with Windows

  8. Universal Data Access - 2 • OLE-DB: DB object linking & embedding • accesses relational databases through ODBC • accesses other data also • files, spreadsheets, e-mail, video, voice, images, web pages, object databases, etc. • data is accessed "in place" (no need to load into a database)

  9. OLE-DB Concepts • data store = "persistent" collection of data • data provider = gets data from data store • OLE-DB "driver" for database, email data, etc. • data consumer = application that uses data • ADO.NET (ActiveX Data Object) interfaces to data store through OLE-DB

  10. ADO.NET • ADO stands for ActiveX Data Objects • part of Microsoft's OLEDB strategy to enable programs to almost any kind of data on a computer • provides objects to easily connect to a variety of data sources • databases, mail servers, http servers, Excel documents, etc.

  11. Using Databases with Internet • web browser interface very easy to use • compatible with all kinds of hardware • Internet is global • low cost delivery to large # of users • multimedia capabilities • ASP.NET can access data through ADO and OLE-DB for web applications

  12. ADO.NET Model Objects • Connection: to a specific file or server • Command: holds/runs SQL/other text to query/update data, call stored procedures, etc. • DataReader: high-speed, limited function interface between database and application

  13. ADO.NET Model Objects - 2 • Data Adapter • uses SQL commands to transfer data back and forth between the application and the database • DataSet • not connected to database • but data can be changed and uploaded • contains one or more DataTables • can "join" multiple tables in DataSet

  14. ADO.NET Model Objects - 3 • DataTables have the following: • DataRowCollection - rows • DataColumnCollection - fields • DataView - use this if need to sort data that is used as a datasource for an object e.g., a datagrid

  15. Database Design • determine functional requirements • identify data required for applications • organize the data • tables (usually normalized) • relationships between tables • identify business rules (middle tier) • design queries and applications

  16. Key Fields • each row in a table is uniquely identified by one or more key field(s) ID# Name City 322 Karim Pomona Dr#Patient# Appointment 397 0246875 10/24/00 2 PM 'key field(s) underlined

  17. Rules for Tables in a Database • all items in each table should relate to one main topic or subject, on a one-to-one basis • employees: SS#, Name, Address, Hourly Pay • paychecks: SS#, Date, Pay Amount • tables should be "normalized" (2NF or more) • no repeated information • no fields that may be intentionally empty • no fields with data that can be calculated (derived) from other fields

  18. Normalization • splitting tables to avoid problems • avoid duplicated data and empty cells • avoid problems: add, change or delete data SID Name GWE ClassQuarter Grade 322 Ana No C101 F99 pass 322 Ana No C234 S00 A • use 2 tables instead • 1-SID, Name, GWE; 2-SID, Class, Quarter, Grade

  19. Normalization - 2 • library has borrowers, books, circulation • put circulation in borrowers file? • repeating patron data for every checked out book Borrower#, Name, Address, Book# • or repeating (often empty) columns Borrower#, Name, Address, Bk#1, Bk#2, etc. • normalize: separate borrowers, circulation Book #, Title, Author, Year, etc. Patron#, Name, Address, etc. Patron#, Book#, Due Date

  20. Specialized Normalized Tables • "parent-child tables" • building: name, address, land area • floor: #, common (non-rentable) area • room: #, square feet • parent table has family name, address • family member table has first names, DOB, gender • "lookup table" • zip, city, state • zip code "determines" city and state • data storage only needs zip • Cerritos mail used to be addressed to Artesia

  21. Denormalization • sometimes more efficient to not completely normalize all tables • less normalization can increase efficiency and possibly reduce number of tables • e.g., 1 customer table with fields for 2 voice phone numbers • only need to update 1 table • don't need to do a join to get all phone #s

  22. Denormalization - 2 • "do not store data in a table if it can be calculated from other data" • e.g., total field (in a separate table) • but with a total field don't need to total a large # of records every time need a total • but do need extra code to update totals when records are added, changed or deleted (as in a "getter" in OO code)

  23. Indexes • data is added to database in random order • more efficient processing for searches and sorting (less efficient for adding data) • index table has sort order (stores position) DataFile OrderIndex/Order Jose (1) 1 (4) Phuong (2) 2 (3) Gunther(3) 3 (1) Ahmed (4) 4 (2)

  24. Creating a Database or Table • using SQL commands with ADO in VB.NET • using VB.NET Server Explorer • using SQL Server Management Studio • using "3rd party" programs • similar to Server Explorer approach or more sophisticated

  25. Creating a Database in Access • Access 2003 new database options • Design View • user needs to type in Field Name, select Data Type, input Field Size and other properties • wizard that provides common templates • entering data manually • uses default settings (like a spreadsheet)

  26. Create Database in Access - 2 • could use File>Get External Data>Import to pull in data from a file, other databases, spreadsheets, etc. • could go into a new table, or be added to an existing table • need to set field properties when bringing in data to a new table e.g., Field Name, Data Type, etc.

  27. SQL Server and Express • Microsoft's SQL Server is designed to handle very large scale applications • more security, transaction logging , stored procedures, very many users, etc. • MSDE (Microsoft Data Engine) is the software that runs SQL Server database • the "engine" in Access is Jet 4.0 (currently) • but Access can read/write MSDE databases

  28. Create SQL Server Express DB • install SSE 2008 • load external data as with SQL Server Management Studio

  29. Using Server Explorer with SSE • View>Server Explorer in VB.NET • click Servers>SQL Servers • right click server that ends with \NETSDK • click (expand) new database • right click Tables>New Table

  30. Using Server Explorer to Create SQL Server Express Database • add fields to master • type in Column Name • type/select Type, Length, etc. • File>Close or right click tab>Close after enter last field • File>Save Table1 and replace name in Choose Name input box

  31. Stored Procedures • code to manipulate database (retrieve data, add, change, delete) stored in database • like subroutine, can use in multiple programs (but not with Access database) • less storage: once instead of multiple copies • easier to update than multiple copies • stored queries run faster inside database • easier to migrate to other platforms or scale up to larger volumes

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