Entity Integrity: There are no duplicate rows in a table.
Domain Integrity: Enforces valid entries for a given column by restricting the
type, the format, or the range of values.
Referential integrity: Rows cannot be deleted, which are used by other records.
User-Defined Integrity: Enforces some specific business rules that do not fall
into entity, domain or referential integrity.
Database Normalization
Database normalization is the process of efficiently organizing data in a database. There
are two reasons of this normalization process:
Eliminating redundant data. For example, storing the same data in more than one
table.
Ensuring data dependencies make sense.
Both these reasons are worthy goals as they reduce the amount of space a database
consumes and ensures that data is logically stored. Normalization consists of a series of
guidelines that help guide you in creating a good database structure.
Normalization guidelines are divided into normal forms; think of a form as the format or
the way a database structure is laid out. The aim of normal forms is to organize the
database structure, so that it complies with the rules of first normal form, then second
normal form and finally the third normal form.
It is your choice to take it further and go to the fourth normal form, fifth normal form and
so on, but in general, the third normal form is more than enough.
First Normal Form (1NF)
SQL
7
Second Normal Form (2NF)
Third Normal Form (3NF)
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