12/4/2001Information Organization and Retrieval Database Design University of California, Berkeley School of Information Management and Systems SIMS 202: Information Organization and Retrieval

12/4/2001Information Organization and Retrieval Last Time Databases and Files Database design Database life cycle Data Models

12/4/2001Information Organization and Retrieval DBMS Benefits Minimal Data Redundancy Consistency of Data Integration of Data Sharing of Data Ease of Application Development Uniform Security, Privacy, and Integrity Controls Data Accessibility and Responsiveness Data Independence Reduced Program Maintenance

12/4/2001Information Organization and Retrieval Database System Life Cycle Growth, Change, & Maintenance 6 Operations 5 Integration 4 Design 1 Conversion 3 Physical Creation 2

12/4/2001Information Organization and Retrieval Database Design Process Conceptual Model Logical Model External Model Conceptual requirements Conceptual requirements Conceptual requirements Conceptual requirements Application 1 Application 2Application 3Application 4 Application 2 Application 3 Application 4 External Model External Model External Model Internal Model

12/4/2001Information Organization and Retrieval Developing a Conceptual Model Overall view of the database that integrates all the needed information discovered during the requirements analysis. Elements of the Conceptual Model are represented by diagrams, Entity- Relationship or ER Diagrams, that show the meanings and relationships of those elements independent of any particular database systems or implementation details.

12/4/2001Information Organization and Retrieval Entity An Entity is an object in the real world (or even imaginary worlds) about which we want or need to maintain information –Persons (e.g.: customers in a business, employees, authors) –Things (e.g.: purchase orders, meetings, parts, companies) Employee

12/4/2001Information Organization and Retrieval Attributes Attributes are the significant properties or characteristics of an entity that help identify it and provide the information needed to interact with it or use it. (This is the Metadata for the entities.) Employee Last Middle First Name SSN Age Birthdate Projects

12/4/2001Information Organization and Retrieval Relationships Relationships are the associations between entities. They can involve one or more entities and belong to particular relationship types

12/4/2001Information Organization and Retrieval Relationships Class Attends Student Part Supplies project parts Supplier Project

12/4/2001Information Organization and Retrieval Types of Relationships Concerned only with cardinality of relationship Truck Assigned Employee Project Assigned Employee Project Assigned Employee 11 n n 1 m Chen ER notation

12/4/2001Information Organization and Retrieval Today Example design (ACME Widget Co.) Normalization (overview)

12/4/2001Information Organization and Retrieval Developing a Conceptual Model We will look at a small business Assume that we have done interviews with the business and found out the following information about the forms used and types of information kept in files and used for business operations...

12/4/2001Information Organization and Retrieval Primary Business Operations The business (ACME Widget Co.) sells parts to customers. –Each part has: A part number, A selling price, A description of the part, The count of the part currently in stock.

12/4/2001Information Organization and Retrieval Business Operations (cont.) Each sale is on an invoice to one customer. –Invoices contain: Line items for each part ordered, Total amount due for the invoice, Customer information: –Company name, address, and an ID number. –Invoices are written up by one sales representative, who is credited with the sale Sales reps are paid a 5% commission on sales.

12/4/2001Information Organization and Retrieval Business Operations (cont.) Information must be kept on inventory of parts. There are multiple suppliers of parts: –The prices charged by different suppliers for a given part may be different. This is the Cost of the part.

12/4/2001Information Organization and Retrieval Business Operations (cont.) Employee information includes: –Name, –Social Security Number, –Employee ID number, –Address, –Position. Hourly wages must be tracked for all employees (except sales reps).

12/4/2001Information Organization and Retrieval Business Operations (cont.) One account is kept for each customer to track charges, payments, and the current balance. The company needs to know if an order has been shipped. The accounting department must know which invoices have been paid. The total sales for each sales rep must be calculated.

12/4/2001Information Organization and Retrieval Business Operations (cont.) We must know if a part is in stock at the company or on order from a supplier. Each hourly employee generates a time-card every Monday morning. Sales Reps don’t turn in time-cards, just their total sales. All employees are paid weekly by check. We need a report each Monday telling us what each employee should be paid for the previous week.

12/4/2001Information Organization and Retrieval Entities Customer Invoice Employee Inventory Supplier Account Sales Rep Parts Timecard Check

12/4/2001Information Organization and Retrieval Functional areas Ordering Inventory Supplies Shipping Personnel Payroll We will concentrate on Ordering and Inventory

12/4/2001Information Organization and Retrieval Ordering Invoice Rep-cust invoice Sales-Rep Customer Simple Ternary Relationship

12/4/2001Information Organization and Retrieval Ordering Invoice Orders Customer Cust# Writes Sales-Rep Invoice# Rep# Parts Repeating attribute

12/4/2001Information Organization and Retrieval Ordering Normalization Orders Customer Cust# Invoice Writes Sales-Rep Invoice# Rep# Line-Item Contains Part# QuantityInvoice# Cust#

12/4/2001Information Organization and Retrieval Parts and Suppliers Part Supplies Supplier Company# Includes Line-Item Part# Count Price Invoice# mn Is this correct? Where does Price belong?

12/4/2001Information Organization and Retrieval Parts and Suppliers (alternative 2) Company# Contains Line-Item Part#Invoice# Part Part# Count Price n m Supplier Company# Offers Supplied-Part Part# Cost Supplies Intersection Entity

12/4/2001Information Organization and Retrieval Parts and Suppliers (Alternative 3) Company# Contains Line-Item Part#Invoice# Part Part# Count Price Supplier Company# Supplies Supplied-Part Part# Cost

12/4/2001Information Organization and Retrieval Parts and Suppliers (Alternative Notation 4) Company# Contains Line-Item Part#Invoice# Part Part# Count Price m Supplier Company# Part# Cost Supplying

12/4/2001Information Organization and Retrieval Parts and Suppliers (Alternative Notation 5) Part Part# Count Price m Supplier Company# Cost Supplies

12/4/2001Information Organization and Retrieval ER Model Orders Customer Cust# Invoice Writes Sales-Rep Invoice# Sales Rep# Line-Item Contains Part# QuantityInvoice# Cust# Contains Part Part#Count Price Supplier Company# Ordered Part Hourly Employee ISA Emp# Wage Company# Part#Cost Supplied Part Has On-Order Supplies Company# Part#Quantity

12/4/2001Information Organization and Retrieval Mapping to a Relational Model Each entity in the ER Diagram becomes a relation. A properly normalized ER diagram will indicate where intersection relations for many-to-many mappings are needed. Relationships are indicated by common columns (or domains) in tables that are related. We will examine the tables for the Acme Widget Company derived from the ER diagram

12/4/2001Information Organization and Retrieval Employee

12/4/2001Information Organization and Retrieval Sales-Rep Hourly

12/4/2001Information Organization and Retrieval Customer

12/4/2001Information Organization and Retrieval Invoice

12/4/2001Information Organization and Retrieval Line-Item

12/4/2001Information Organization and Retrieval Part

12/4/2001Information Organization and Retrieval Joins

12/4/2001Information Organization and Retrieval Normalization Normalization theory is based on the observation that relations with certain properties are more effective in inserting, updating and deleting data than other sets of relations containing the same data Normalization is a multi-step process beginning with an “unnormalized” relation

12/4/2001Information Organization and Retrieval Normal Forms First Normal Form (1NF) Second Normal Form (2NF) Third Normal Form (3NF) Boyce-Codd Normal Form (BCNF) Fourth Normal Form (4NF) Fifth Normal Form (5NF) Others (rarely used)

12/4/2001Information Organization and Retrieval Normalization Boyce- Codd and Higher Functional dependencyof nonkey attributes on the primary key - Atomic values only Full Functional dependencyof nonkey attributes on the primary key No transitive dependency between nonkey attributes All determinants are candidate keys - Single multivalued dependency

12/4/2001Information Organization and Retrieval Unnormalized Relations First step in normalization is to convert the data into a two-dimensional table In unnormalized relations data can repeat within a column

12/4/2001Information Organization and Retrieval ACME Unnormalized

12/4/2001Information Organization and Retrieval First Normal Form To move to First Normal Form a relation must contain only atomic values at each row and column. –No repeating groups –A column or set of columns is called a Candidate Key when its values can uniquely identify the row in the relation.

12/4/2001Information Organization and Retrieval ACME 1NF

12/4/2001Information Organization and Retrieval 1NF Storage Anomalies Insertion: A new custome has not yet bought anything -- hence no sales_rep -- Since sales_rep is part of the key we can’t insert. Insertion: If a sales_rep is newly hired and hasn’t sold any widgets yet -- there will be no way to include that person in the database. Update: If a customer places a new order, and has moved, we need to change multiple address entries. Deletion (type 1): Deleting customer information may also delete all info about a sales_rep. –Or deleting information about an employee may remove all information about a customer

12/4/2001Information Organization and Retrieval Second Normal Form A relation is said to be in Second Normal Form when every nonkey attribute is fully functionally dependent on the primary key. –That is, every nonkey attribute needs the full primary key for unique identification –This is achieved by splitting up the tables…

12/4/2001Information Organization and Retrieval ACME 2NF EMPLOYEE CUSTOMER SALES_REP INVOICE LINE-ITEM PARTS

12/4/2001Information Organization and Retrieval 1NF Storage Anomalies Removed Insertion: Can now enter new sales_reps without them selling anything. Insertion: Can now enter customers who haven’t ordered anything yet. Deletion (type 1): If Fred Rogers quits, the corresponding tuples from Employee and Sales_rep tables can be deleted without losing information on Consolidated Brands. Update: If General Consolidated places a new order and has moved, we only need to change the Customer table in one place

12/4/2001Information Organization and Retrieval Third Normal Form A relation is said to be in Third Normal Form if there is no transitive functional dependency between nonkey attributes –When one nonkey attribute can be determined with one or more nonkey attributes there is said to be a transitive functional dependency. All of our tables are already in 3NF.

12/4/2001Information Organization and Retrieval Boyce-Codd Normal Form Most 3NF relations are also BCNF relations. A 3NF relation is NOT in BCNF if: –Candidate keys in the relation are composite keys (they are not single attributes) –There is more than one candidate key in the relation, and –The keys are not disjoint, that is, some attributes in the keys are common

12/4/2001Information Organization and Retrieval Fourth Normal Form Any relation is in Fourth Normal Form if it is BCNF and any multivalued dependencies are trivial Eliminate non-trivial multivalued dependencies by projecting into simpler tables

12/4/2001Information Organization and Retrieval Fifth Normal Form A relation is in 5NF if every join dependency in the relation is implied by the keys of the relation Implies that relations that have been decomposed in previous NF can be recombined via natural joins to recreate the original relation.

12/4/2001Information Organization and Retrieval Relational Algebra Operations Select Project Product Union Intersect Difference Join Divide

12/4/2001Information Organization and Retrieval Select Extracts specified tuples (rows) from a specified relation (table).

12/4/2001Information Organization and Retrieval Project Extracts specified attributes(columns) from a specified relation.

12/4/2001Information Organization and Retrieval Join Builds a relation from two specified relations consisting of all possible concatenated pairs of, one from each of the two relations, such that in each pair the two tuples satisfy some condition. A1 B1 A2 B1 A3 B2 B1 C1 B2 C2 B3 C3 A1 B1 C1 A2 B1 C1 A3 B2 C2 (Natural or Inner) Join

12/4/2001Information Organization and Retrieval Outer Join Outer Joins are similar to PRODUCT -- but will leave NULLs for any row in the first table with no corresponding rows in the second. A1 B1 A2 B1 A3 B2 A4 B7 B1 C1 B2 C2 B3 C3 A1 B1 C1 A2 B1 C1 A3 B2 C2 A4 * * Outer Join

12/4/2001Information Organization and Retrieval Relational Calculus Relational Algebra provides a set of explicit operations (select, project, join, etc) that can be used to build some desired relation from the database. Relational Calculus provides a notation for formulating the definition of that desired relation in terms of the relations in the database without explicitly stating the operations to be performed SQL is based on the relational calculus.

12/4/2001Information Organization and Retrieval SQL Structured Query Language SEQUEL from IBM San Jose ANSI 1992 Standard is the version used by most DBMS today (SQL92) Basic language is standardized across relational DBMSs. Each system may have proprietary extensions to standard.

12/4/2001Information Organization and Retrieval SQL Uses Database Definition and Querying –Can be used as an interactive query language –Can be imbedded in programs Relational Calculus combines Select, Project and Join operations in a single command. SELECT.

12/4/2001Information Organization and Retrieval SELECT Syntax: –SELECT [DISTINCT] attr1, attr2,…, attr3 FROM rel1 r1, rel2 r2,… rel3 r3 WHERE condition1 {AND | OR} condition2 ORDER BY attr1 [DESC], attr3 [DESC]

12/4/2001Information Organization and Retrieval SELECT Conditions = equal to a particular value >= greater than or equal to a particular value > greater than a particular value <= less than or equal to a particular value <> not equal to a particular value LIKE “*term*” (may be other wild cards in other systems) IN (“opt1”, “opt2”,…,”optn”) BETWEEN val1 AND val2 IS NULL

12/4/2001Information Organization and Retrieval Relational Algebra Selection using SELECT Syntax: –SELECT * WHERE condition1 {AND | OR} condition2

12/4/2001Information Organization and Retrieval Relational Algebra Projection using SELECT Syntax: –SELECT [DISTINCT] attr1, attr2,…, attr3 FROM rel1 r1, rel2 r2,… rel3 r3

12/4/2001Information Organization and Retrieval Relational Algebra Join using SELECT Syntax: –SELECT * FROM rel1 r1, rel2 r2 WHERE r1.linkattr = r2.linkattr

12/4/2001Information Organization and Retrieval Sorting SELECT PARTS.NAME, PARTS.PRICE FROM PARTS ORDER BY PARTS.PRICE DESC;

12/4/2001Information Organization and Retrieval Subqueries SELECT EMPLOYEE.NAME, EMPLOYEE.BIRTHDATE FROM EMPLOYEE WHERE EMPLOYEE.SSN IN (SELECT SSN FROM SALES_REP WHERE SALES_REP.SALES > 14000) ; Can be used as a form of JOIN.

12/4/2001Information Organization and Retrieval Aggregate Functions Count Avg SUM MAX MIN

12/4/2001Information Organization and Retrieval Using Aggregate functions SELECT attr1, Sum(attr2) AS name FROM tab1, tab2... GROUP BY attr1, attr3 HAVING condition;

12/4/2001Information Organization and Retrieval Effectiveness and Efficiency Issues for DBMS Focus on the relational model Any column in a relational database can be searched for values. To improve efficiency indexes using storage structures such as BTrees and Hashing are used But many useful functions are not indexable and require complete scans of the the database

12/4/2001Information Organization and Retrieval Example: Text Fields In conventional RDBMS, when a text field is indexed, only exact matching of the text field contents (or Greater-than and Less- than). –Can search for individual words using pattern matching, but a full scan is required. Text searching is still done best (and fastest) by specialized text search programs (Search Engines) that we will look at more later.

12/4/2001Information Organization and Retrieval Normalizing to death Normalization splits database information across multiple tables. To retrieve complete information from a normalized database, the JOIN operation must be used. JOIN tends to be expensive in terms of processing time, and very large joins are very expensive.

12/4/2001Information Organization and Retrieval Advantages of RDBMS Possible to design complex data storage and retrieval systems with ease (and without conventional programming). Support for ACID transactions –Atomic –Consistent –Independent –Durable

12/4/2001Information Organization and Retrieval Advantages of RDBMS Support for very large databases Automatic optimization of searching (when possible) RDBMS have a simple view of the database that conforms to much of the data used in businesses. Standard query language (SQL)

12/4/2001Information Organization and Retrieval Disadvantages of RDBMS Until recently, no support for complex objects such as documents, video, images, spatial or time- series data. (ORDBMS are adding support these). Often poor support for storage of complex objects. (Disassembling the car to park it in the garage) Still no efficient and effective integrated support for things like text searching within fields.