Creating databases for web applications New example: last lecture Systems design. ER diagrams. Data flow diagrams. Storyboards. Homework: Plan database and applications for a library: produce ERD and DFD

Added example Students: name, gpa, department Go to last lecture for code http://newmedia.purchase.edu/~Jeanine/db/studentexample/showstudents.php http://newmedia.purchase.edu/~Jeanine/db/studentexample/showdepartments.php http://newmedia.purchase.edu/~Jeanine/db/studentexample/enterstudent.html

System analysis and design Tools for planning communication with clients (specific diagrams may not always be shown, but used to support discussion) communication with builders Attempt to focus on function before implementation logical design versus physical design non-tech meaning of term Historically, a problem with computer work has been the rush to implementation, independent of understanding of desired function.

Models Information model = Entity relationship diagrams Ask yourself: what is the critical information? What are the relationships (what fields in one table point to other records?) Process model = data flow What are the (main) processes? Who initiates these processes? What data stores are used and/or changed? Story board What are the Web pages—the interfaces to the user (client/player/employee)? What is the flow from one Web page to another? There are other modeling schemes, for example, object oriented modeling.

ER models Done before creating the tables as part of planning and after creating the tables, as documentation Logical/analysis level (what is in examples here) just defines fields and relationships. Physical/Design/Implementation level: data types and also estimates on number of records. I'm trying to use all the terms typically used.

Entity-relationship Entity = the things (products, people, places, business concepts) attributes = fields = properties Relationships = connections between things, as represented by a field in one table (attribute of an entity) pointing to an entity.

Primary keys and foreign keys A field (attribute) that uniquely defines a record in a table can be its primary key. sometimes generated automatically by dbms In another table, the way to refer to this record would be by using the primary key value. This is called a foreign key in that other table.

Entity Relationship diagrams Blocks represent the records in the table. Typically, they list all the fields. Lines between the blocks represent relationships. The marks on the lines indicate the numbers, e.g., one to many, one to one. They also indicate what a minimum would be. 0 means that an entity in one table may not be referenced in the other at all.

Example: trivia quiz Tables are Questions Players History (that is, a question was asked [of] a player on a specific date, with outcome correct or not correct Each item in History relates to a specific player and a specific question

Question databank table question_id Question Answer (answer pattern) Players table player_id Player name Score lastplayed date Question databank table question_id Question Answer (answer pattern) Value Category history table question_id player_id whenplayed correct ER diagram for quiz show. Note: the history table has relations with each of the other two tables. The primary key of the history table is the pair: question_id and player_id.

Course pre-req example In this design, each course has at most one pre-requisite course.

Course course title Division Pre-requisite simple version: only works if there are only 0 or 1 pre-requisites. However, a course can be a pre-requisite for zero or many courses.

Course pre-reqs, more complete Each course can have no, 1, or any number of pre-requisites. TWO TABLES! Courses Statements of pre-reqs

Statement of pre-requisites Course to be taken pre-required course (prior course) Course Course title Division Each statement of pre-requisites refers to exactly one course and exactly one 'pre-req'. A course can be in either position, zero, one or several times. Creating Web Documents is a pre-req for Creating Dynamic Web Docs & Creating DBs for Web Some courses may have pre-requisites of more than one course. The second example may not be true. In fact, Purchase registration does not monitor or enforce ANY pre-requisites! This could be even more complicated: pre-requisites may be satisfied by one of several courses….

clip tag table Video archive application has table of clips and tags similar to the pre-req tables. Demonstrate NOTE: I removed entries on 2 videos and then restored them with shorter names!

Data design Sometimes done by taking the artifacts (forms, reports, screens) and writing down all those fields into first draft of records These artifacts can be from the current system or the proposed materials for a new system Apply a technique called normalization to get well-defined entities and relationships. First step is making sure each record has fixed number of fields. For example, not indefinite number of pre-reqs Subsequent steps ensure that data is not repeated, so information only needs to be updated in one place Make customer data be in a customer file NOT in each transaction file EXTRA CREDIT opportunity for posting We may cover this later in course.

Process diagram Focus on Blocks Connections processes agents (this could be people in specific roles or 'the system' triggered by events, including a time condition) data stores: more general term than databases Connections Agent engaged with process Process using data store This approach can be modified to an event driven approach.

Player Questions DB Play game History DB Edit questions Player scores Data flow diagram (process diagram) for quiz show Player Questions DB Play game History DB Edit questions Player scores Data flow diagram (process diagram) for quiz show Editor

Story board more implementation based than the others Therefore, part of system build, not system design, or, perhaps, System Physical Design not Logical Design focus on the scripts and how the scripts call each other Story board is term from advertising, animation, ?

Include/Required file: opendbq Create quiz tables (php only) Input Questions (handles form input) Choose category Show scores Ask question Story board. Thicker Links with round bases represent handling of form. Names are readable versions of file names. Check answer Clear tables

Entities for store Initial design catalog of products orders one or more ordered items customer list Enhanced design Need 1 more table: call it ordered items Normalization would tell you you need a 4th entity for the ordered items distinct from the orders. Since I've done this many times before, I know to do this.

Customer list Customer ID first name last name Billing information ER diagram for on-line store Customer list Customer ID first name last name Billing information E-mail Password Product catalog Product id Product name Picture Cost Order list Order ID Customer ID Date Status Total Ordered items Order ID Product Quantity ER diagram for on-line store. The connectors, often called crow’s feet, indicate the cardinality, the possible numbers of the relationships: each ordered item relates to exactly 1 product and exactly one order. Each order is for exactly one customer. However, a customer can have zero or more orders. An order includes at least one ordered item (the 1 is indicated by the vertical line.)

Billing system (timed event) Data flow (process) diagram for on-line store. Catalog Browse/Order Customer Customer list Billing Current orders Ordered items Shipping Billing system (timed event) Data flow (process) diagram for on-line store. Note that this is the information/data flow, not the flow of goods. The orange indicates processes and associated agents NOT implemented in the example I will present. Note: this diagram does not distinguish between the (personal) shopping cart, which is a list of items, and the ordered items for all customers. Shipping clerk Note that this is the information/data flow, not the flow of goods. The shipping operation produces a physical product: the collection of ordered items, packed and set off for delivery.

Create tables (php only) Include/require: opendbo Storyboard of partial implementation: ordering Create tables (php only) Include/require: opendbo Input products Delete current customer cookie Order product Story board. Thicker Links with round bases represent handling of form. Names are readable versions of file names. makeorder Submit order Shopping cart Include/require: displaycartfunction

Video archive: main table $fields = "fileaddr varchar(15) NOT NULL,cliptitle varchar(50) NOT NULL,"; $fields = $fields . "clipdate varchar(10),clipgroup varchar(15), sequence int(6), PRIMARY KEY (fileaddr)"; NOTE: example of primary key NOT created by DBMS.

Video archive: tag table $fields = "fileaddr varchar(15) NOT NULL,tag varchar(20) NOT NULL";

ER for video clip archive Video clips File addr Clip title Clip group Sequence Tags File addr Tag

Grid Design example Designs generated in Flash application stored as variable length strings in database Alternative would be to store design elements, like the ordered items Application could use sign on procedure!

ER for design Members Member id Member name Member email Member password Designs Design id Member id Design name Design string

Song with features example Bare bones Song table and Feature table plus A song can have 0 or more features Intention is to provide way of detecting songs similar to a given song Complex SQL statement!

Song features feature id name description song id Name Description Year feature of song fisid fid

Song with features storyboard createtables.php deletefeaturesinsongs.php listallfeaturesinsongs.php addsong.html addsong.php opendbe.php (included in all php files) addfeature.html addfeature.php addfeaturestosong1.php addfeaturestosong2.php findothers1.php findothers2.php

Songs with features DFD Add songs Identify songs Admin Finder Song info Add feature Add features to song Edit info

Agents Of course in these toy applications such as the songs with features, there is just one agent (me!) but Important to plan what are roles of system builders versus system users Some social networking song sites do allow users to add songs, specify features, add features, etc.

Opportunity for improvement Functions mentioned but not implemented (in orange) Navigation could be better specifically, going back or 'coming out of' steps. Where to go Teams will review and enhance these projects and present whole thing to the class. Mike noted that problems with navigation.

Homework Design ER and DFD for a library. YOUR job is to define entities, relationships, agents, data stores, processes. Logical design, not physical design Note: a data store could be manual. Don't be concerned with that.