DataBase Normalization Short Note, Study notes of Computer science

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Normalization

What is Normalization

Normalization is the process of minimizing redundancy from a

relation or set of relations. Redundancy in connection can

cause insert, delete and update anomalies. Hence, it helps

to reduce redundancy in relationships. Normal formats are

used to eliminate or reduce redundancy in database tables.

The purpose of Normalisation in SQL is to eliminate

redundant ( repetitive ) data and ensure data is stored

logically.

Normalization

A relation is in first normal form if it has a composite or multi-valued property

that violates first normal form or if there is no composite or multi-valued property. A relation is in first normal form if every attribute of that relation is a valued attribute. 1NF FORM RULE ● Each tablemust contain cell a single value. ● Each record mustbe unique.

Normalization

To be incontain any partial dependency. A relation is in 2NF if it has second normal form , a relation must be in first normal form and relation must not No Partial Dependency , i.e., no non-prime attribute (attributes whichproper subset of any candidate key of are not part of any candidatethe table. Partial Dependency (^) – If the proper subset ofkey) is dependent on any candidate key determines non-prime attribute, it is called partial dependency. 2NF FORM RULE ● Rule 1-1NF Stay in ● Rule 2-column primarySingle keyfunctionally that does not dependsubset onof anythe candidaterelation key

Keys

Aused to uniquely key in SQL is a value identify records in KEY is a single column or a table. A SQL combination of columns usedto uniquely identify rows orkey tuples in is used to identify a table. SQL duplicate informationit also helps to establish and relationshipmultiple tables in between the database. Note:that are not Columns in used to a table uniquely identify a recordare called non-key columns.

https://www.javatpoint.com/dbms-keys Shashikala Madumali

Primary Keys

A primary is a single column value used to identify a database record uniquely. It has the following attributes ● ● A primary keyA primary key cannotvalue must be NULL be unique ● ● TheThe primary key valuesprimary key must be should given rarelya value be when changed a new record is inserted.

Foreign Key references the primary key of another Table! It helps connect your tables ● ● AIt ensures foreign key rows can in have one atable different name from its primary key have corresponding rows in another ● ● UnlikeForeign the keys primary can be null key, they even do though primary keys cannot not have to be unique. Most often they aren't

Foreign Keys

Additional notes

https://opentextbc.ca/dbdesign01/chapter/chapter-12-normalization/ https://www.marwaricollegeranchi.ac.in/pdf/Blog/ch04-Normalization.pdf https://www.javatpoint.com/dbms-keys https://www.emsisd.com/cms/lib/TX21000533/Centricity/Domain/71/Database_Terminology_an d_Concepts.pdf https://www.amplifyre.com/articles/ultimate-guide-relational-databases