Brief Intro to relational databases

Size: px

Start display at page:

Download "Brief Intro to relational databases"

Hannah Blair
5 years ago
Views:

1 Brief Intr t relatinal databases A relatinal database cnsists f tables Tables cnsist f rws and clumns, which can als be referred t as recrds and fields A table is typically mdeled after a real-wrld entity, such as a curse r an instructr A clumn represents sme attribute f the entity, such as a list f curses r an instructr s address A rw cntains a set f values fr ne instance f the entity, such as ne curse r ne instructr Example (simplified UVA CS curse inf) Curse_inf cursename title prerequisite descriptin units CS1111 Intrductin t Prgramming Nne 3 CS2910 CS Educatin Practicum New TAing 1 CS4640 Prgramming Languages fr Web Applicatins CS The intersectin f a rw and a clumn is smetimes called a cell, string a single value Mst tables have a primary key that uniquely identifies each rw in the table The primary key is usually a single clumn, but it can als cnsist f tw r mre clumns In additin t primary keys, mst database management systems (DBMS) allw ne r mre nn-primary key CREATE TABLE Curse_inf ( cursename VARCHAR(12) PRIMARY KEY, title VARCHAR(255) NOT NULL, prerequisite VARCHAR(255) NOT NULL, descriptin VARCHAR(255) NOT NULL, units INT NOT NULL) (cursename, title, prerequisite, descriptin, units) VALUES ('CS1111','Intrductin t Prgramming','Nne','descriptin fr CS1111',3) (cursename, title, prerequisite, descriptin, units) VALUES ('CS2910', 'CS Educatin Practicum','New TAing','descriptin fr CS2910',1) (cursename, title, prerequisite, descriptin, unit`) VALUES ('CS4640', 'Prgramming Languages fr Web Applicatins','2150','descriptin fr CS4640',3)

2 Example (simplified UVA CS curse inf) Curse_inf cursename title prerequisite descriptin units CS1111 Intrductin t Nne 3 Prgramming CS2910 CS Educatin Practicum New TAing 1 CS4640 Prgramming Languages fr Web Applicatins CS Instructr_inf cmputingid name department up3f Upsrn Praphamntripng up3f@virginia.edu Cmputer Science Schedule classnumber cursename cmputingid DateTime Lcatin CS1111 up3f MWe 2:00pm - 3:15pm Thrntn Hall E CS2910 up3f TuTh 12:30pm - 1:45pm Rice CS2910 up3f Th 11:15am 12:00pm, Fr 3:00pm-3:45pm Rice 536, Olssn CS4640 up3f TuTh 2:00PM - 3:15PM Clark Hall 108 Freign key Freign key CREATE TABLE Instructr_inf ( cmputingid VARCHAR(12) PRIMARY KEY, name VARCHAR(255) NOT NULL, VARCHAR(255) NOT NULL, department VARCHAR(255) NOT NULL ) INSERT INTO Instructr_inf (cmputingid, name, , department) VALUES ('up3f','upsrn Praphamntripng','up3f@virginia.edu','Cmputer Science')

3 CREATE TABLE Schedule ( classnumber VARCHAR(5) NOT NULL PRIMARY KEY, cursename VARCHAR(12) NOT NULL, cmputingid VARCHAR(12) NOT NULL, DateTime VARCHAR(255) NOT NULL, Lcatin VARCHAR(255) NOT NULL, FOREIGN KEY (cursename) REFERENCES Curse_inf(curseName), FOREIGN KEY (cmputingid) REFERENCES Instructr_inf(cmputingID) ); VALUES ('15783','CS1111','up3f','MWe 2:00pm - 3:15pm','Thrntn Hall E303') VALUES ('16636','CS2910','up3f','TuTh 12:30pm - 1:45pm','Rice 340') VALUES ('20294','CS2910','up3f','Th 11:15am 12:00pm, Fr 3:00pm-3:45pm','Rice 536, Olssn 001') VALUES ('16639','CS4640','up3f','TuTh 2:00PM - 3:15PM','Clark Hall 108') The tables in a relatinal database are related t each ther thrugh their key clumns. Fr example, the cursename clumn is used t related the Schedule table and Curse_inf table The cursename clumn in the Schedule table is called a freign key because it identifies a related rw in the Curse_inf table. The cmputingid clumn in the Schedule table is called a freign key because it identifies a related rw in the Instructr_inf table Allw data retrieval frm multiple tables SELECT Schedule.classNumber, Schedule.curseName, Curse_inf.title, Instructr_inf.name, Schedule.DateTime, Schedule.Lcatin FROM Schedule, Curse_inf, Instructr_inf WHERE Schedule.curseName = Curse_inf.curseName AND Schedule.cmputingID = Instructr_inf.cmputingID ORDER BY Schedule.curseName When defining a freign key, yu can t add rws t the table with the freign key unless there s a matching primary key in the related table The relatinships between the tables in a database crrespnd t the relatinships between the entities they represent. The mst cmmn type f relatinship is a ne-t-many relatinship (shwn in the example) A table can als have a ne-t-ne relatinship r a many-t-many relatinship with anther table

4 T use PHP with a MySQL database Refer t in-class 9: Establish a cnnectin // T cnnect t a MySQL database named web4640, need three arguments: // - specify a DSN, username, and passwrd // DSN (Data Surce Name) specifies the hst cmputer fr the MySQL database // and the name f the database. If the MySQL database is running n the same server // as PHP, use the lcalhst keywrd t specify the hst cmputer $dsn = "mysql:hst=$hstname;dbname=$dbname"; // Create an instance f PDO (PHP Data Objects) which cnnects t a MySQL database // (PDO defines an interface fr accessing databases) $db = new PDO($dsn, $username, $passwrd); Nte: Yu may write cde t cnnect t the database and d manipulatin in the same.php file, r Yu may write cde t cnnect t the database as an external cmpnent When using an external php prgram t cnnect t the database, a require() is recmmended <?php // require('cnnect-db.php'); // require: if a required file is nt fund, require() prduces a fatal errr, the rest f the script wn't run // include: if a required file is nt fund, include() thrws a warning, the rest f the script will run?> Prepare a query $query = "sme-sql-statement"; $statement = $db->prepare($query); Execute a query $statement->execute(); Free the cnnectin t the server s ther SQL statements may be issued $statement->clsecursr();

T use the MVC pattern t rganize PHP cde The MVC (Mdel-View-Cntrller) pattern is cmmnly used t structure web applicatins that have significant prcessing requirements and thus making them easier t cde

5 T use the MVC pattern t rganize PHP cde The MVC (Mdel-View-Cntrller) pattern is cmmnly used t structure web applicatins that have significant prcessing requirements and thus making them easier t cde and maintain The mdel cnsists f the PHP files that represent the data f the applicatin The view cnsists f the HTML and PHP files that represent the user infrmatin f the applicatin The cntrller cnsists f the PHP files that receive requests frm users, get the apprpriate data frm the mdel, and return the apprpriate views t the users

IMPORTING INFOSPHERE DATA ARCHITECT MODELS INFORMATION SERVER V8.7

IMPORTING INFOSPHERE DATA ARCHITECT MODELS INFORMATION SERVER V8.7 Prepared by: March Haber, march@il.ibm.cm Last Updated: January, 2012 IBM MetaData Wrkbench Enablement Series Table f Cntents: Table f