Introduction CSC 330 Object Oriented Programming C# and Databases Introduction to Database Management System What are Databases?

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1 CSC 330 Object Oriented ming C# and Databases Database: Introduction Integrated collection of data Database management system (DBMS) Provides mechanisms for storing and organizing data in a way that is consistent with database s format Allows storage and access to database without knowledge of internal representation Relational Databases most popular Use Structured Query Language to perform queries (search) and manipulate data ming languages need an interface to interact with relational databases 2 Introduction to Database Management System What are Databases? A database management system (DBMS) is software that manages large collections of data It is designed to store, retrieve, and manipulate data A C# application can interact with a DBMS through a 3-layer manipulation Application: interacts with the user and sends instructions to DBMS DBMS: works directly with the data and sends the result back to the application Data: the data stored in DBMS Application DBMS Features of DBMS Definition of data structure Maintenance facility Allow access to and storage of data independently of the internal representation of data Main job of the DBMS is to ensure data integrity Data 3 4 Relational Database Systems and SQL Relational database systems are the most popular today (Microsoft Access is a relational database system) SQL is international standard language used with relational database systems to perform queries (i.e. to request information that satisfies given criteria) and to manipulate data Some popular relational database management systems (RDBMS) are Microsoft SQL Server, Oracle, MySQL, Sybase Relational Database Model Logical representation of data: Relationships can be considered without concern for physical structure of data Composed of tables Rows called records Columns called fields Primary key: field that contains unique data Each record can be identified by at least one distinct value New sets made from queries called result sets 5 6 1

2 Tables, Rows, and Columns Data stored in a database are organized into tables, rows, and columns Each table holds a collection of related data A table is a two-dimensional container made of rows and columns A row is a complete set of information about a single item A column holds an individual piece of information about the item Column Data Types When you create a database table, you must specify a data type for the column Acceptable data types are defined by DBMS, not C# SQL Server Description Corresponding C# or.net Framework Data Type Data Type bit True/false values bool datetime A date and a time DateTime decimal(t, d) A decimal value with t total digits and d digits appearing after the decimal point. decimal Name Phone float Real numbers double int An integer number int Each row contains data about one person Katie Allen Jill Ammons Kevin Brown Elisa Garcia Jeff Jenkins money Values that represent currency decimal nchar(n) A fixed-length Unicode string with a maximum length of n characters. string nvarchar(n) A variable-length Unicode string with a maximum length of n characters. string 7 8 Relational Database Model All information is contained in tables (or relations) Tuple or row (record) Attribute or column (field) Relationships [not why called relational] Relation Instance The current values (relation instance) of a relation are specified by a table An element t of r is a tuple, represented by a row in a table customer_name customer_street customer_city attributes (or columns) Jones Smith Curry Lindsay Main North North Park Harrison Rye Rye Pittsfield tuples (or rows) customer 9 10 Relational Database Model Relationships are logical representation of data: Not concerned with physical structure Primary key: field that contains unique data Each record can be identified by at least one distinct value record/row number name department salary location Jones New Jersey Kerwin New Jersey Larson Los Angeles Myers Orlando Neumann New Jersey Stephens Orlando Primary Keys Most database tables have a primary key A primary key is a column that can be used to identify a specific row The column that is designated as the primary key must hold a unique value for each row. For example, Employee ID, social security number, invoice number, sales order number Sometimes the data that you want to store in a table does not contain any unique items that can be used as a primary key You need to create an identity column specifically to serve as the primary key. This column is known as an identify column. Identify columns typically contain integers Each time a new row is added to the table, the DBMS automatically assigns a unique value to the identify column primary key field/column

3 Primary Keys Relational DBMS enforces several constraints on data Rule of Entity Integrity: in most cases every record has a unique value in its primary- key field Primary key does not have to be a single field Compound Primary Key: when a record has a unique key based on a combination of two fields Foreign Keys A foreign key is used to create relationships: Field for which every entry has a unique value in another table and where the field in the other table is the primary key for that table Rule of Referential Integrity: every foreign- key field value must appear in another table s primary- key field One to many relationship: A foreign key can appear many times in its own table, but only once as primary key in another table Rule of Entity Integrity: in most cases every record every record hasa unique value in its primary-key field Compound Primary key: when a record has a unique key based on a combination of two fields Foreign key: Field for which every entry has a unique value in another table and where the field in the other table is the primary key for that table Rule of Referential Integrity: every foreign-key field value must appear in another table s primary-key field One to many relationship: A foreign key can appear many times in its own table, but only once as primary key in another table Fie ld authorid firstname Desc rip tion Author s ID number in the database. In the Books database, this int field is defined as an auto-incremented field. For each new record inserted in this table, the database increments the authorid value, ensuring that each record has a unique authorid. This field represents the table s primary key. Author s first name (a string). lastname Author s last name (a string). Fig Authors table from Books Fig Data from the Authors table of Books. 17 Field publisherid publishername Fig Description The publisher s ID number in the database. This auto-incremented int field is the table s primary-key field. The name of the publisher (a string). Publishers table from Books. publisherid publishername 1 Prentice Hall 2 Prentice Hall PTG Fig Field authorid Data from the Publishers table of Books. Desc rip tion The author s ID number, which allows the database to associate each book with a specific author. The integer ID number in this field must also appear in the Authors table. isbn The ISBN number for a book (a string). Fig AuthorISBN table from Books. 18 3

4 authorid isbn authorid isbn x x x Fig Data from AuthorISBN ta b le in Books. 19 Fie ld isbn title editionnumber copyright publisherid imagefile price Fig Desc rip tion ISBN number of the book (a string). Title of the book (a string). Edition number of the book (a string). Copyright year of the book (an int). Publisher s ID number (an int). This value must correspond to an ID number in the Publishers table. Name of the file containing the book s cover image (a string). Suggested retail price of the book (a real number). [Note: The prices shown in this database are for example purposes only.] Titles table from Books. 20 Fig part 1 isbn title edition- publish- copyright imagefile price Number erid P y th o n H o w to 1 1 python.jpg $69.95 C# H ow to cshtp.jpg $69.95 J a v a H o w to jhtp4.jpg $69.95 The Complete Java javactc4.jpg $ A dvanced Java advjhtp1.jpg $69.95 Platform H ow to Intern et and W orld iw3htp2.jpg $69.95 W ide W eb How to V isual B asic.n ET vbnet.jpg $69.95 H o w to P r o g r a m T h e C o m p le t e C cppctc3.jpg $ T he C om p lete e ebecctc.jpg $ B usiness & e- C o m m e r c e m ing X The C om plete iw3ctc2.jpg $ Intern et & W orld W ide W eb m ing The Complete Perl perl.jpg $ The Complete xmlctc.jpg $ XM L m ing 21 Fig part C H ow to chtp3.jpg $ C++ How to cpphtp3.jpg $69.95 e-business X and e ebechtp1.jpg $69.95 C om m erce H ow to W ireless Internet wireless.jpg $69.95 an d M ob ile B usiness H ow to Perl H ow to perlhtp1.jpg $69.95 XM L How to xmlhtp1.jpg $69.95 The C om plete iw3ctc1.jpg $ Intern et and W orld W id e W eb ming Training C ourse Java H ow to jhtp3.jpg $69.95 Pro gram (Java 2 ) The Complete Java javactc3.jpg $ Training C ourse e-business and e ebecm.jpg $69.95 C om m erce for M a n a g ers Intern et and W orld iw3htp1.jpg $69.95 W id e W eb H o w to G etting S tarted gsvc.jpg $49.95 with Visual C++ 6 with an Intro du ctio n to M F C 22 Fig part The Complete vbctc1.jpg $ Visual Basic 6 Visual Basic vbhtp1.jpg $69.95 How to Java M ultim edia javactc.jpg $ Cyber Classroom The Entity- relationship diagram for the Book database Java How to jhtp1.jpg $ The Complete C cppctc2.jpg $ C++ How to cpphtp2.jpg $49.95 The Complete Java javactc2.jpg $ The Complete Java javactc2.jpg $99.95 (Java 1.1) Java How to jhtp2.jpg $49.95 (Java 1.1) C++ How to cpphtp1.jpg $ C How to chtp2.jpg $ C How to chtp.jpg $69.95 Authors authorid firstname lastname 1 AuthorISBN authorid isbn 1 Publishers publisherid publishername Titles isbn title editionnumber copyright 1 publisherid imagefile price Fig Da ta fro m the Titles table of Books

5 Relational Database Queries Queries : return a new result set Based upon relational algebra Uses 3 operations to build a new relation (a result-set) Projection, selection, and join What is SQL? Structured Query Language (SQL) Keywords and rules used to implement relational algebra operations SQL Keywords Basic Select Query SQL ke yw o rd SELECT FROM WHERE INNER JOIN GROUP BY ORDER BY INSERT UPDATE DELETE Fig SQL query keywords. Description Selects (retrieves) fields from one or more tables. Specifies tables from which to get fields or delete records. Required in every SELECT and DELETE statement. Specifies criteria that determine the rows to be retrieved. Joins records from multiple tables to produce a single set of records. Specifies criteria for grouping records. Specifies criteria for ordering records. Inserts data into a specified table. Updates data in a specified table. Deletes data from a specified table. Extracts information from one or more tables in a database Format: Basic: select * from table-name select * from authors * means "extract all columns" To get a projection (specific columns), use a list: select firstname, lastname from authors Column, table names may be case sensitive SQL keywords should not be case sensitive Basic Select Query Where Clause authorid lastname authorid lastname 1 Deitel 8 McPhie 2 Deitel 9 Yaeger 3 Nieto 10 Zlatkina 4 Steinbuhler 12 Wiedermann 5 Santry 12 Liperi 6 Lin 13 Listfield 7 Sadhu Fig authorid and lastname from the Authors table. 29 Used to specify certain criteria in a query Basic form: SELECT * FROM tablename WHERE criteria SELECT * FROM Titles WHERE copyright > 1999 Can use LIKE clause Used for pattern matching Uses wildcards *: zero or more characters take its place?: exactly one character takes its place 30 5

6 Pattern-matching with Where Can use like clause for string pattern matching Uses wildcards %: zero or more characters take its place (*) _: exactly one character takes its place (?) Examples: Select * from authors where firstname like '_e%' Select * from authors where lastname like 'D%' 31 WHERE Clause Title editionnumber copyright Internet and W orld W ide W eb H ow to P rogram Java How to The Complete Java The Complete e-business & e-commerce ming T h e C o m p le te In te rn e t & W o rld W id e W eb m ing The Complete Perl The Complete XM L m ing C How to C++ How to The Complete C e-business and e-com m erce How to Internet and W orld W ide W eb H ow to P rogram The Com plete Internet and W orld W ide W eb m ing Java How to (Java 2) The Complete Java XM L How to P erl H ow to P rogram Advanced Java 2 Platform How to e-business and e-com m erce for M anagers W ireless Internet and M obile Business How to C# How To Python How to V isu al B asic.n E T H o w to P ro g ram Fig Title s w ith c o p yrig h ts a fte r 1999 fro m ta b le Titles. 32 WHERE Clause Sorting the Results Fig Authors from the Authors ta b le w ho se last na m es sta rt w ith D. Fig Authors from table Authors whose last names contain i as the second letter. SQL queries return their data in indeterminate order Same query may return rows in different order each time Use the order by clause to arrange results of a query Can be ascending (asc) or descending (desc) order Examples: select * from authors order by lastname desc select * from authors order by lastname, firstname asc ORDER BY Clause Used to arrange results of a query Can be ascending or descending order Uses ASC and DESC respectively SELECT authorid FROM Authors ORDER BY authorid ASC Can be used to sort by multiple fields 35 ORDER BY Clause Fig Authors from table Authors in ascending order by lastname. 36 6

7 ORDER BY Clause Fig Authors from table Authors in descending order by lastname. 37 ORDER BY Clause Fig Authors from table Authors in ascending order by lastname and by firstname. 38 ORDER BY Clause isbn title edition- copyright price Number Advanced Java 2 Platform 1 $69.95 How to Merging Data from Multiple Tables: INNER JOIN Merges records from multiple tables into a single record Tests for matching values in a common field C How to $ C How to $ C How to $ C# How To $ C++ How to $49.95 General Form: C++ How to $ C++ How to $69.95 select * from table X e-b usiness and e-com m erce $69.95 How to Internet and W orld W ide W eb $69.95 inner join table 2 on table1.field = table2.field How to Internet and W orld W ide W eb $69.95 How to Java How to $ Java How to $49.95 select firstname, isbn from Perl How to $ Python H ow to $69.95 authors inner join authorisbn Visual Basic.NET How to $69.95 Visual Basic How to $69.95 on authors.authorid = authorsisbn.authorid W ireless In te rnet and M ob ile $69.95 B usiness H ow to XML How to $69.95 Books from table Titles w hose titles end w ith How to in Fig a sc e n d in g o rd e r b y title. 40 Merging Data from Multiple Tables: INNER JOIN firstname lastname isbn firstname lastname isbn Harvey D eitel Harvey D eitel Harvey D eitel Harvey Deitel Harvey D eitel Paul Deitel Harvey D eitel Paul Deitel Harvey D eitel Paul Deitel Harvey D eitel Paul Deitel x Harvey D eitel x Paul Deitel Harvey D eitel Paul Deitel Harvey D eitel Paul Deitel Harvey D eitel Paul Deitel Harvey D eitel Paul Deitel Harvey D eitel Paul Deitel Harvey D eitel Tem Nieto Paul D eitel Tem Nieto Paul D eitel Paul D eitel Paul D eitel Tem Nieto Paul D eitel Tem Nieto Paul D eitel x Paul D eitel Fig A utho rs fro m ta b le Authors and ISBN num bers of the authors books, sorted in ascending order by lastname and firstname. 41 Joining Data from Tables Authors, AuthorISBN,, Titles and Publishers Tables produced by INNER JOIN can be used as arguments for another INNER JOIN 42 7

8 Joining Data from Tables Authors, AuthorISBN, Titles and Publishers 1 SELECT Titles.title, Titles.isbn, Authors.firstName, 2 Authors.lastName, Titles.copyright, 3 Publishers.publisherName 4 FROM 5 ( Publishers INNER JOIN Titles 6 ON Publishers.publisherID = Titles.publisherID ) 7 INNER JOIN 8 ( Authors INNER JOIN AuthorISBN 9 ON Authors.authorID = AuthorISBN.authorID ) 10 ON Titles.isbn = AuthorISBN.isbn 11 ORDER BY Titles.title Join two created tables if titlesisbn matches authorsisbn Fig TitleAuthor query of Books database. Join Publishers and Titles tables if the publisherid matches Join Authors and AuthorISBN if authorid matches Sort new table by title Fig part 1 Joining Data from Tables Authors, AuthorISBN, Titles and Publishers Title isbn first- last- copyright publisher- Name Name Name Advanced Java 2 Platform Paul Deitel 2002 Prentice H all How to Advanced Java 2 Platform Prentice H all How to Advanced Java 2 Platform Sean Santry 2002 Prentice H all How to C How to Harvey Deitel 1992 Prentice H all C How to Paul Deitel 1992 Prentice H all C How to Harvey Deitel 1994 Prentice H all C How to Paul Deitel 1994 Prentice H all C How to Harvey Deitel 2001 Prentice H all C How to Paul Deitel 2001 Prentice H all C# How To Tem Nieto 2002 Prentice H all C# How To Paul Deitel 2002 Prentice H all C# How To Jeffrey Listfield 2002 Prentice H all C# How To Cheryl Yaeger 2002 Prentice H all C# How To Marina Zlatkina 2002 Prentice H all C# How To Harvey Deitel 2002 Prentice H all C++ How to Paul Deitel 2001 Prentice H all Fig part 2 Joining Data from Tables Authors, AuthorISBN, Titles and Publishers C++ How to Harvey Deitel 2001 Prentice Hall C++ How to Paul Deitel 1994 Prentice Hall C++ How to Harvey Deitel 1994 Prentice Hall C++ How to Harvey Deitel 1998 Prentice Hall C++ How to Paul Deitel 1998 Prentice Hall for Managers for Managers for Managers How to How to How to Harvey Deitel 2000 Prentice Hall Kate Steinbuhl er 2000 Prentice Hall Paul Deitel 2000 Prentice Hall X Harvey Deitel 2001 Prentice Hall X Paul Deitel 2001 Prentice Hall X Tem Nieto 2001 Prentice Hall Fig Portion of the result set produced by the query in Fig The Selection Operation The selection operation is accomplished using where Basic form: select * from table-name where criteria select * from titles where copyright > 1999 Make sure String criteria are inside single quotes Can use expected relational operators select * from authors where firstname > 'B' SQL and Relational Operators with the Where Clause SQL String Functions SQL supports several relational operators for writing conditional expressions Operator Meaning > Greater than < Less than >= Greater than or equal to <= Less than or equal to = Equal to <> Not equal to SQL keywords and clauses are not case-sensitive. But, string comparison are. Denim Jeans, denim jeans, and Denim jeans are considered three different string literals The following three SQL statements will generate three different results: SELECT * FROM Product WHERE Description = Denim Jeans SELECT * FROM Product WHERE Description = denim jeans SELECT * FROM Product WHERE Description = Denim jeans You can use the Lower() or Upper() string function before performing the comparison SELECT * FROM Product WHERE Lower(Description) = denim jeans SELECT * FROM Product WHERE Upper(Description) = DENIM JEANS

9 Using the LIKE Operator Sorting the Results of a Select Query The LIKE operator allows you to do a search based on a pattern rather than specifying exactly what is desired Oxford Cloth Shirt and Poplin Shirt both contains the string Shirt Use the string Shirt as the pattern with the wildcard character % % represents any sequence of zero or more characters SELECT * FROM Product WHERE Description LIKE %Shirt% SELECT * FROM Product WHERE Description LIKE Chino% SELECT * FROM Product WHERE Description LIKE %jeans The underscore (_) wildcard character represents a single character. To search for all rows in which Product_Number begins with 2, followed by any one character, followed by -0, followed by any one character, use SELECT * FROM Product WHERE Product_Number LIKE 2_-0_ To sort the results of a SELECT query, use the ORDER BY clause SELECT * FROM Product ORDER BY Price SELECT * FROM Product WHERE Price > ORDER BY Price The results will be sorted in ascending order To sort in descending order, use the Desc operator SELECT * FROM Product ORDER BY Price Desc SELECT * FROM Product WHERE Price > ORDER BY Price Desc Insert Statement Inserts a new record into a table General form: insert into table-name(fieldname1, fieldname2,...) values(value1, value2) insert into authors(authorid, lastname, firstname) values(15, 'Gilbert', 'Steve') Values must match field names in order and type 51 INSERT Statement 14 Sue Smith Fig Authors after an INSERT operation to add a record. 52 The Update Statement Modifies data in a table General Form: update table-name set field1=value1 where criteria update authors set firstname='stephen' where lastname='gilbert' and firstname='steve' What happens if you violate an integrity rule? 53 UPDATE Statement 14 Sue Jones Fig Table Authors after an UPDATE operation to change a record. 54 9

10 The Delete Statement Removes data from a table General Form: delete from table-name where criteria Don't forget the criteria!!! delete from authors where lastname='gilbert' DELETE Statement Fig Table Authors after a DELETE operation to remove a record SQL Math Functions Creating a Database in Visual Studio SQL provides several functions for performing calculations Avg(Column): calculates the average value in a particular column SELECT Avg(Price) FROM Product Sum(Column): calculates the sum of a column s values SELECT Sum(Price) FROM Product Min(Column): finds the minimum value of a column. SELECT Min(Price) FROM Product Max(Column): finds the maximum value of a column SELECT Max(Price) FROM Product Count(Column): returns the number of values of the specified column SELECT Count(Price) FROM Product To determine the number of rows in a table, use: SELECT Count(*) FROM Product A.NET application uses several components, arranged in layers, to connect to a database Data Source a source of data with which the application can work Table Adapter connects to a data source and retrieves data from a table in a data source Dataset gets a copy of a table from the table adapter and keeps the copy of the table in memory Binding Source a component that can connect user interface controls directly to a dataset Application Binding Source Dataset Table Adapter Data Source Creating A Server-Based Database The Database File s Location Visual Studio provides wizards that make it easy to create and configure the database The Add New Item window provides a Service-based Database option for creating an empty SQL Server database The default name of the SQL Server database is Database1.mdf This book uses SQL Server database as examples When you use Visual Studio to create a SQL server database, the database file will be created in the project s folder The project s folder is where the Form1.cs, Form1.Designer.cs, and.cs files are stored The file extension is.mdf. For example, Phonelist.mdf. The server will also create a file that ends with the.ldf extension. For example, Phonelist_log.LDF. This is a transaction log file used to keep a log of all the operations that you perform on the database