BUS1MIS Management Information Systems Semester 1, 2012 Access: Creating a Database Week 6 Lecture 2 In this lecture the key ideas are: • A broad understanding of a relational database is important knowledge for business managers. • A relational database organises data into multiple related tables. • An effective relational database minimises data redundancy. Also included will be: • An overview of creating a relational database in Microsoft Access 2007 At the core of a Management Information System is a database (or many databases) The key component of a database is a table. Customer Table Field Customer ID Customer Name Customer Address Customer Phone 6512 Jones Bendigo 5444888 7989 Singh Catlemaine 5442777 9112 Ng Echuca 5967222 Record A table stores data about some entity in the real world. For example, customers, orders, items of stock. A table has rows and columns like a spreadsheet. Each column describes an attribute of the entity. For example, customer name, customer address. An individual column in a table is called a field. Each row describes an instance of the entity. For example, a customer, an order, an item of stock. An individual row in a table is called a record. Comparison between a database table and a spreadsheet A blank spreadsheet is an open book. You can add whatever you want in whatever structure you want. A database table has a predefined structure. Each row in the table has an identical structure. A business manager needs the knowledge to be confident that the database underlying an important MIS has been correctly designed by the IT person responsible. If a database is not correctly designed the data may be…… • poorly organised and/or • incomplete and/or • inaccurate and/or • duplicated …. then management will receive poor quality reports and poor decisions are likely to be made. What is the correct design for a database? Let’s try “simple is best” first and put all our data in the one table. See the next slide for the example to be used in the lecture CJC’s Images Order Form Order #: 1927 Order Date: 12/5/09 Customer Name: Liam Customer Address: Brisbane Item # Item Name Qty Ordered 3720 Large Framed 3 2917 Small Unframed 6 1129 Small Framed 1 Let’s design a single table to store this data Order # Order Date Cust. Name Cust. Item# Address Item Name Quantit y 1927 12/5/09 Liam Brisbane 3720 LFramed 3 1927 12/5/09 Liam Brisbane 2917 SUnframed 6 1927 12/5/09 Liam Brisbane 1129 SFramed 1 Assume there are other orders as well 1928 13/5/09 Kirsty Sydney 1129 SFramed 2 1928 13/5/09 Kirsty Sydney 1800 LUFramed 15 1929 14/5/09 Liam Brisbane 3720 LFramed 1 1929 14/5/09 Liam Brisbane 2917 SUFramed 1 1929 14/5/09 Liam Brisbane 1129 SFramed 1 1929 14/5/09 Liam Brisbane 1800 LUFramed 1 If Liam changes address, how many changes need to be made to the table? Putting all our data in a single table means we have ended up with ……. Data Redundancy …. the scourge of all database design. How do we avoid data redundancy in our database design? Most business databases use a relational database design. The database consists of multiple, related tables Any piece of data is only stored ONCE If we apply a relational database design to the Order Form in the previous slide we would have 4 related tables. Cust Name Cust Address Order # Item # Quantity Liam Brisbane 1927 3720 3 Kirsty Sydney 1927 2917 6 1927 1129 1 1928 1129 2 Item # Item Name 1129 SFramed 1928 1800 15 1800 LUFramed 1929 3720 1 2917 SUFramed ……… …… … 3720 LFramed Order # Order Date Cust Name 1927 12/5/09 Liam 1928 13/5/09 Kirsty 1929 14/5/09 Liam If Liam changes address, how many changes need to be made to the database? To maintain the links between the tables we need … 1.A field in each table which uniquely identifies each record (called a primary key) 2.Some software to maintain the links The primary key is nearly always a number, as in a Student ID. The software to create the tables and maintain the links is known as a Database Management System (DBMS) We will be using Microsoft Access as a DBMS.