Sometimes is BCNF is also referred as 3. Report a Bug. Previous Prev. Next Continue. Home Testing Expand child menu Expand. SAP Expand child menu Expand. Web Expand child menu Expand. Must Learn Expand child menu Expand. Big Data Expand child menu Expand. Live Project Expand child menu Expand. AI Expand child menu Expand. Toggle Menu Close. Search for: Search. Note the multiple Class values for each Student value in the above table.
Class is not functionally dependent on Student primary key , so this relationship is not in second normal form. In the last example, Adv-Room the advisor's office number is functionally dependent on the Advisor attribute. The solution is to move that attribute from the Students table to the Faculty table, as shown below:. Feedback will be sent to Microsoft: By pressing the submit button, your feedback will be used to improve Microsoft products and services.
Privacy policy. Skip to main content. This browser is no longer supported. Download Microsoft Edge More info. Contents Exit focus mode. Is this page helpful? Yes No. Any additional feedback? Skip Submit. Normalization is a systematic approach of decomposing tables to eliminate data redundancy repetition and undesirable characteristics like Insertion, Update and Deletion Anomalies.
It is a multi-step process that puts data into tabular form, removing duplicated data from the relation tables. The video below will give you a good overview of Database Normalization. If you want you can skip the video, as the concept is covered in detail, below the video. If a table is not properly normalized and have data redundancy then it will not only eat up extra memory space but will also make it difficult to handle and update the database, without facing data loss.
Insertion, Updation and Deletion Anomalies are very frequent if database is not normalized. To understand these anomalies let us take an example of a Student table. In the table above, we have data of 4 Computer Sci. Suppose for a new admission, until and unless a student opts for a branch, data of the student cannot be inserted, or else we will have to set the branch information as NULL. Also, if we have to insert data of students of same branch, then the branch information will be repeated for all those students.
What if Mr. For the second normal form , the relation must first be in 1NF. The relation is automatically in 2NF if, and only if, the PK comprises a single attribute. If the relation has a composite PK, then each non-key attribute must be fully dependent on the entire PK and not on a subset of the PK i. To be in third normal form , the relation must be in second normal form. Also all transitive dependencies must be removed; a non-key attribute may not be functionally dependent on another non-key attribute.
At this stage, there should be no anomalies in third normal form. The first step is to remove repeating groups, as discussed above. To recap the normalization process for the School database, review the dependencies shown in Figure When a table has more than one candidate key, anomalies may result even though the relation is in 3NF. Boyce-Codd normal form is a special case of 3NF. A relation is in BCNF if, and only if, every determinant is a candidate key.
T he semantic rules busines s rules applied to the database for this table are:. The functional dependencies for this table are listed below. The first one is a candidate key; the second is not. During the normalization process of database design, make sure that proposed entities meet required normal form before table structures are created.
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