User:Auró/sandbox 3

Basics

Basically a data base is a table containing information organized in columns and rows. Table 1 below is a simple instance of a database.

Table 1

Purchase order	Customer	Product	Quantity
180901	Arex	TV monitor HD	100
180902	Betro	Amplifier PS	50
180903	Cartin	Tuner HF	200
180904	Arex	Amplifier PS	60
180905	Betro	TV monitor HD	150

Instead of having this table, we could have the same information contained in two different tables as these.

Table 2 (Purchase order)

Purchase order	Product	Quantity
180901	TV monitor HD	100
180902	Amplifier PS	50
180903	Tuner HF	200
180904	Amplifier PS	60
180905	TV monitor HD	150

Table 3 (Customer table)

Customer	Purchase order
Arex	180901
Arex	180904
Betro	180902
Betro	180905
Cartin	180903

The second arrangement is more efficient for the purposes of managing the information. These two tables contain a common column (purchase order), that is the key that makes possible to connect and ralate both tables, hence the term relational data bases.