CPSC 603 Database Systems Lecturer: Laurie Webster II, Ph.D., P.E. Introduction to a First Course in Database Systems

CPSC 603 Database Systems What is a Database Management System? Manages very large amounts of data Supports efficient access to very large amounts of data Supports concurrent access to v.l.a.d Supports secure, atomic access to v.l.a.d

Relational Database Systems CPSC 603 Database Systems Relational Database Systems Ted Codd in 1970 wrote a famous paper “A Relational Model for large shared data banks” => database systems changed significantly!!

CPSC 603 Database Systems Database Systems presented Users with a View of data organized as tables called Relations In this course we will concentrate primarily on Relational Models of Database Systems

Relational Model (Table) CPSC 603 Database Systems Relational Model (Table) acct# name balance 12345 Sally 1000.21 34567 Sue 245.48 ……. …….. …...

Relational Model (Table) CPSC 603 Database Systems Relational Model (Table) * Today Relational Models are used in most DBMS’s * The columns of relations (tables) are headed by attributes (acct#, name, balance, type,….)

Relational Model (Table) CPSC 603 Database Systems Relational Model (Table) Rows of the relations(tables) are also called tuples Tuples are a mathematical term

Relational Model (Table) Columns Tuples Rows CPSC 603 Database Systems Relational Model (Table) Columns Tuples Rows

SQL => Structured Query Language CPSC 603 Database Systems SQL => Structured Query Language SELECT A1, A2, ………., An FROM r1, r2, ………….., rm WHERE p Relational Algebra A1, A2, ……., An ( p (r1, r2, ………….., rm ) ) p  predicate , Ai  attributes , ri  relations

CPSC 603 Database Systems attributes account balance type 12345 1000.00 savings rows (tuples) 67890 2846.92 checking …….. ………. ………. …… => many more tuples, one for each account at this bank!!! CPSC 603 Database Systems

CPSC 603 Database Systems attributes Accounts accountNo balance type 12345 1000.00 savings rows (tuples) 67890 2846.92 checking …….. ………. ………. SELECT balance FROM Accounts WHERE accountNo = 67890; QUERY: What is the balance of account number 67890 ? CPSC 603 Database Systems

CPSC 603 Database Systems SQL QUERY => SELECT account FROM Accounts WHERE type = ‘savings’ AND balance < 0; QUERY: What are the saving accounts with negative balances?

CPSC 603 Database Systems SQL QUERY => SELECT account FROM Accounts WHERE type = ‘savings’ AND balance < 0; 1. Examine all tuples of the relation Accounts mentioned in the FROM - clause 2. Pick out those tuples that satisfy some criterion indicated in the WHERE clause, and 3. Produce as an answer certain attributes of those tuples, as indicated in the SELECT - clause.

CPSC 603 Database Systems Major Components of a DBMS: Query Processor Storage Manager Data + Metadata Transaction Manager Metadata = information about the structure of the data If the DBMS is relational then the metadata includes the names of relations, names of attributes, data types for these attributes (e.g., integer or character string of length 20)

Schema Modifications Queries Modifications Query Processor Transactions Manager Storage Manager Data Metadata

CPSC 603 Database Systems DATA MODELS * Underlying structure of a database is the data model structure => data types, relationships, constraints that should hold for the data

Data Models Object-based logical models Record-based logical models Physical models

Object-Based Logical Model Entity-Relationship model (ER Models) The Object-Oriented model The Semantic Data Model The Functional Data Model

E-R Data Models E-R Model is based on a perception of a real world that consists of a collection of basic objects called entities and of relationships among these objects Entity is a “thing” or “object” in the real world that is distinguishable from other objects i.e. a person is an entity Relationship is an association among several objects

Object-Oriented Model Object-Oriented Models are based on a collection of objects

Record-Based Logical Model Relational Model (primary focus of this class) Network Models Hierarchical Model