Database Fundamentals. Why use a database?. Putting all data into a single file simply doesn’t work because- Redundancy Insertion/deletion/update problems when all data is in a single file Data integrity (data can’t be trusted) . Why must a database be “normalized?” .
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Putting all data into a single file simply doesn’t work because-
Normalization is just a fancy word for “putting the data into tables that make sense and will not cause errors.”
A data model is like an architectural blueprint for a database. It shows-
Cardinality is the numerical relationship between tables. It is need to show how the occurrence of one record in a table relates to other tables.
For example, a customer order may have many orders but a particular order can only refer to 1 customer. An order can only be associated with one customer but a particular customer can have many orders.
This is shown as 1:M
A particular customer may have 0 or many orders in the orders table. A particular order can only be related to a one and only one customer.
Most cardinalities (the numerical relationship between tables) in a database are-
1:M (one to many)
The one to one cardinality (1:1) is rarely needed but it is sometimes used for the following reasons-
A poorly constructed data model will likely result in bad data and unintended actions occurring in the database.