1 Database & DBMS The data that goes into transaction processing systems (TPS), also goes to a database to be stored and processed later by decision support systems (DSS) or other information systems (see next 2 slides). Information (processed data) can also be stored in a database. The size of database is huge as some organizations store data up to 20 years, e.g. government, banks. Crucial to have the huge database managed properly; database management systems (DBMS) can help e.g. Access, Oracle, DB2, FoxPro, Sybase.

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3 Functional Management Information Systems Draw Data from the Organization’s TPS

4 Database Terminologies A database - a collection of tables. Tables are also called relations. 2-dimensional table: a series of row/column intersections –A table represents one type of entity e.g. a table for agents, and a separate table for customers. –A table contains related entities of a particular type, e.g. a table of different customers’ records, a table of different agents’ records.

5 Relational Database Model Figure 1.11

6 Relational Database Attribute (a column or a field) of a table –An attribute is one characteristic (or property) of that type of entity e.g. customer’s address, phone number, sex, birth date etc. Record (a row) of a table –Represents a particular entity e.g. a particular customer or a particular agent. –Has logically connected fields that describe a particular entity e.g. a person, place, a thing, an object, a concept or thing about which data are collected.

7 Relational database Each entity must have a unique key or identifier. Tables must have an attribute(s) that uniquely identify each row (or entity) – primary key. Values of a column all have the same data format. The order of the rows and columns is immaterial (unimportant) to the DBMS e.g. Microsoft Access. Primary key of each table must: –Be Unique –Have No ‘null’ value in key –consist of a single field or multiple fields. –E.g. HKID, car registration number.

8 Relationship between ‘Agent’ and ‘customer’ ‘Agent’ and ‘customer’ are 2 separate entity types (in 2 different tables). ‘Agent’ and ‘customer’ have a 1-to-many relationship because of the following: - Each ‘agent’ is in charge of 1 or more ‘customers’, but each ‘customer’ only deals with 1 particular ‘agent’.

9 Relational Database Schema See next slide – a relational schema produced by Microsoft access. The “AGENT_CODE” is the unique identifier for each agent. The “CUS_CODE” is the unique identifier for each customer. Here, “CUSTOMER” represent the “many” side, because an agent can have many customers. The “AGENT” represents the “1” side because each customer has only a single agent.

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11 Simple Relational Database Figure 2.2

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13 Keys Primary key –to uniquely identify an entity from many entities of the same type. Foreign key –Values must match primary key in another table –Used to have relationships (1:1, 1:M or M:N) with another table.

14 Example 1:M Relationship Figure 2.20

15 Database Design and schema IT professionals and programmers are responsible for the design (schema) of the database: table structures, relationships between tables, primary and foreign keys etc. Business managers or users of a database should understand the design of a database and query this database for information or data. Use Access’s QBE to query a simple database.