Business computing

Business computing

Databases (3)

13 january 2004

Databases are containers for structured data

• In business we mostly work with structured data• The data are organised into several tables

– The tables are the containers of the data

• The data are displayed in forms and reports• I.e. the functions « store the data » and « display

the data » are separate• That is why in databases we are often

wondering « where is the data ? », because the organisation is not intuitive

Structured information

• A body of information is structured when it is made of very many items with the same structured information on each

• For instance : an address book

• For instance : 830 orders received and treated over the course of 3 years by a sales dept

Classroom examples

• Last time we constructed a two table database containing the information of an address book

• Today we shall study bdcomptoir.mdb : an example created and distributed by Microsoft to illustrate the possibilities of Access

• It contains the information on 3 years of orders of a food wholesaler

bdcomptoir.mdb

• It is a database (that is a container of data) from the sales dept of a wholesaler of food

• It contains all the sales data over 3 years of sales, order by order (830 orders)

• For each order, it contains– Building blocks : Sub-order per product– Quantities, client, supplier, sales clerk, date,

etc…

Architecture of bdcomptoir.mdb

• bdcomptoir.mdb is a classroom example of what Access can do, distributed by Microsoft

• The designers of bdcomptoir.mdb chose to organise the data into eight tables :– A central table the records of which are elementary

blocks of orders (2155 elementary blocks)– And 7 other tables : Orders, Clients, Products,

Suppliers, Categories, Messengers, Sales clerks)

Bdcomptoir and Bd_ex2

• The logic of the distribution of information into different tables is the same for bdcomptoir and for bd_ex2

• Just (a bit) more complicated

• If we understand well bd_ex2 it becomes easy to understand bdcomptoir

Learning databases

• Just like we learn Accounting not to become accountants, but to be able to understand accounting reports

• We learn databases not to become databases specialists, but to be able to manage databases specialists work, and understand what they can do

Multi-table databases

• Whenever the same information appears again and again on many different records of one table it should be stored into another table, and related to the first table with a link

• In our small « address book » database, persons is one table, cities is another one, and departments can be made into a third one

Purpose

• Monitor the activity of the sales department :– Obtain summary information on clients– Same on products,– On suppliers– Make marketing plans– Manage our sales team– …be as efficient as possible (cf. Amazon)– And make as much profit as possible…

Amazon

• When we ask information about one particular book on Amazon, Amazon tells us which other books clients, interested in this book, bought : efficient use of a sales information system

Chosen architecture for bdbomptoir.mdb

• The architects of bdcomptoir chose to create a first table of elementary information, made of PARTS of each order

• Each order contains several lines, one line per product

• These lines will form the « basic table » with 2155 records

• All the remaining information will be organised into « satellite tables » (7 of them)

Basic table of « building blocks »

• In the address book database the « basic table » is « persons » (7 persons)

• Cities (and departments) are listed in another table, linked to « persons »

• In bdcomptoir the basic table is « détails commandes » (2155 items, building blocks of orders), it is linked to « products » and to « commandes », and these in turn are linked to other tables

Basic table of « building blocks » (2)

• In the table « persons » we have cities mentioned, but no information about department. That information is in the table « cities »

• In the table « detail commandes » we have only five fields (order number, product, price, quantity, rebate)

• Everything else (on clients, suppliers, category, clerk, etc.) is in other tables

Basic table of « building blocks » (3)

• These are considerations on how the data are stored

• It says nothing of how the data are displayed : indeed we can display data the way we like

• Do not confuse « storing » and « displaying »

Displays

• The two main ways to display data from a database are– Forms (also used to enter data)– Reports, to create standard documents

Exports

• Information displayed can be exported into other Office softwares

• For example a report can be exported into a Word document

Imports

• Well organized information into an Excel sheet can be imported into an Access database

Dynamic link Excel/PPT

name firstname city deptjean dupont lille 59jacques durant tourcoing 59marie dubois paris 75athanase plastiras poitiers 86lisetta coirault poitiers 86andre cabannes lille 59marie laforet tourcoing 59bernard machin paris 75

Asking questions to a database

• Two ways– The simple way : use a filter– The more elaborate (and more powerful)

way : construct a query

Use of bdcomptoir.mdb

• Filter, queries, and reports

• We can « ask questions » to the database

• And we can also produce « reports »

• For example : – How many times the product « chang » was

ordered ?– What total quantity of « chang » product did

we sell ?