1nf, 2nf, 3nf and bcnf in database normalization _ dbms tutorial _ studytonight

Database Normalisation is a technique of organizing the data in the database. Database functions Normalization is a systematic approach of decomposing tables to eliminate data redundancy and undesirable characteristics like Insertion, Update and Deletion Anamolies. Top 10 data recovery It is a multi-step process that puts data into tabular form by removing duplicated data from the relation tables.


Without Normalization, it becomes difficult to handle and update the database, without facing data loss. Database job titles Insertion, Updation and Deletion Anamolies are very frequent if Database is not Normalized. Data recovery linux live cd To understand these anomalies let us take an example of Student table. S pombe database S_id

• Updation Anamoly : To update address of a student who occurs twice or more than twice in a table, we will have to update S_Address column in all the rows, else data will become inconsistent.

• Insertion Anamoly : Suppose for a new admission, we have a Student id(S_id), name and address of a student but if student has not opted for any subjects yet then we have to insert NULL there, leading to Insertion Anamoly.

• Deletion Anamoly : If (S_id) 401 has only one subject and temporarily he drops it, when we delete that row, entire student record will be deleted along with it.

As per First Normal Form, no two Rows of data must contain repeating group of information i.e each set of column must have a unique value, such that multiple columns cannot be used to fetch the same row. Database usa Each table should be organized into rows, and each row should have a primary key that distinguishes it as unique.

The Primary key is usually a single column, but sometimes more than one column can be combined to create a single primary key. Data recovery pro license key For example consider a table which is not in First normal form

In First Normal Form, any row must not have a column in which more than one value is saved, like separated with commas. Data recovery on android Rather than that, we must separate such data into multiple rows.

Using the First Normal Form, data redundancy increases, as there will be many columns with same data in multiple rows but each row as a whole will be unique. Icare data recovery 94fbr Second Normal Form (2NF)

As per the Second Normal Form there must not be any partial dependency of any column on primary key. Image database It means that for a table that has concatenated primary key, each column in the table that is not part of the primary key must depend upon the entire concatenated key for its existence. Database web application If any column depends only on one part of the concatenated key, then the table fails Second normal form.

In example of First Normal Form there are two rows for Adam, to include multiple subjects that he has opted for. Database graphic While this is searchable, and follows First normal form, it is an inefficient use of space. In databases a category of data is called a Also in the above Table in First Normal Form, while the candidate key is { Student, Subject}, Age of Student only depends on Student column, which is incorrect as per Second Normal Form. Database wordpress To achieve second normal form, it would be helpful to split out the subjects into an independent table, and match them up using the student names as foreign keys.

In Subject Table the candidate key will be { Student, Subject} column. Note 2 data recovery Now, both the above tables qualifies for Second Normal Form and will never suffer from Update Anomalies. Tally erp 9 data recovery Although there are a few complex cases in which table in Second Normal Form suffers Update Anomalies, and to handle those scenarios Third Normal Form is there. Database erd Third Normal Form (3NF)

Third Normal form applies that every non-prime attribute of table must be dependent on primary key, or we can say that, there should not be the case that a non-prime attribute is determined by another non-prime attribute. Database google docs So this transitive functional dependency should be removed from the table and also the table must be in Second Normal form. Database 5500 For example, consider a table with following fields.

In this table Student_id is Primary key, but street, city and state depends upon Zip. Data recovery kit The dependency between zip and other fields is called transitive dependency. Database meaning Hence to apply 3NF, we need to move the street, city and state to new table, with Zip as primary key.

Boyce and Codd Normal Form is a higher version of the Third Normal form. Gale database This form deals with certain type of anamoly that is not handled by 3NF. Data recovery pc A 3NF table which does not have multiple overlapping candidate keys is said to be in BCNF. Data recovery easeus For a table to be in BCNF, following conditions must be satisfied:

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