1NF,2NF, 3NF Normalization

If you want to know more about normalization and keys refer this posts:

http://vinayjallipalli75996.blogspot.in/2016/12/different-type-of-keys-in-database.html

http://vinayjallipalli75996.blogspot.in/2016/12/normalization-in-database.html





1NF : Composite attribute are not allowed.

2NF: All non prime attributes are fully functional dependent with primary key.that is non prime attributes should not be partially dependent on primary key.

3NF: There should not be any dependency between non prime attributes.
             
Example For 3NF (see the below fig.): student id,name, dob , street,city, zip,state->>>
                       1)sid,name,dob
                       2)zip, city, state, Street becoz zip is dependent on rest of the three.



Comments

Post a Comment

Popular posts from this blog

Different Type of keys in Database Managemenet System.

Image
All super, candidate and primary, secondary keys are used to uniquely distinguish all rows in data base. But the main difference between them is. Super 🔑 -superset of candidate keys Candidate 🔑 -subset of super key, it is a single key or least combination of feild that uniquely  identifies every tuple. Primary 🔑- it is a candidate key that is most appropriate to become main key for the table. Secondary 🔑- candidate keys which are not selected as primary keys. Non-key attributes (attributes other than candidate keys) Non prime attributes (attributes other than primary key) Foreign 🔑?? It is a feild in one table that uniquely identifies a row in another table They are constraints between column of tables. Example:
Read more

FC Barcelona vs Real Madrid -El Clasico Rivalry.

Image
                              El Clasico The Story of the Rivalry between FC Barcelona and Real Madrid  The rivalry comes about as  Madrid  and  Barcelona  are the two largest cities in Spain, and they are sometimes  identified  with opposing political positions, with Real Madrid viewed as representing  Spanish nationalism  and Barcelona viewed as representing  Catalan nationalism . It is considered one of the biggest club  football  games in the world, and is among the most viewed annual sporting events.  It has always been a heated match, from both sides. Political background: The rivalry between the the two most successful clubs in football started with an oft-ignored political backstory and contrasts in how both clubs were made.  FC Barcelona was founded by --> Joan Gamper along with several foreign-...
Read more

Normalization in Database.

Image
What is normalisation in simple terms?? The process of organising data into columns and tables such as to reduce redundancy in the data is called normalisation. And to avoid insert, delete, and update anomalies. From ☝ answer many of you know about redundancy but not anomalies,  So what is a anomaly? Anomalies are problems that can occur in Poorly planned, un-normalised databases where all the data is stored in one table (a flat-file database). There are 3 types of anomalies  insert anomaly delete anomaly update anomaly I will explain the above with a simple example instead of explaining them with formal defnitions. Consider the below table. From the above table : Redundancy: When ever i add a student of cse department, the information about the department(i.e department name, hod and phone number) is repeating as you can see in above table. This redundancy should be reduced when you normalize the database. Insert anomaly: If i want to ...
Read more