0
A functional dependency occurs between two attributes in a database, A and B, if there exists a relationship such that for each value of A there is only one corresponding value of B (A -> B). This can be extended to a functional dependency where A may be a set of tuples (x, y, z) that correspond to a single value B ([x, y, z] -> B). In simple mathematical terms the functional dependency must pass the vertical line test for proper functions. Normalization of a relational database means that the relations (tables) in the database conform to a set of rules for a certain normal form (First - Sixth Normal Form [1-6NF] and/or Boyce-Codd Normal Form [BCNF]). The higher the normal form of a table the less vulnerable it is to data inconsistency and data anomalies formed during updates, inserts, and deletes. Normalization often reduces data redundancy in a database which reduces data inconsistency and anomaly risks. Normalizing a database requires analysis of the closure of the set of functional dependencies to ensure that the set complies with the rules for the given normal form. If the table does not comply with the rules then the table is split following specific procedures to achieve the desired normal form. Every table in a database has a normal form and to make a statement that a database is in a certain normal form (ex. 3NF) means that every table complies with the rules for 3NF.
Wiki User
∙ 14y ago
Add your answer:
Earn +20 pts
Fully functional dependency?
A functional dependency X --> Y is full functional dependency if removal of any attribute 'k' from X means that the dependency does not hold any more.Full functional dependency is minimal in size (contain non-redundant data)In a relation R , attribute B of R is fully functionallydependent on an attribute or set of attributes A of R , if B is functionally dependent on A, but not functionally dependent on any proper subset of A.ORAàB is a fully functionally dependency, if removal of any attribute X from A would result into the cancellation of dependency. i.e. (A-{X})-->B does not hold.
What is important to consider when creating a database?
Memory should be taken into account when building a database and maintain integrity and avoid redundancy through normalization.
What is the purpose of using joins in database is normalization the only purpose of it?
The purpose of using Normalization is to avoid the data redundancy in tables. The normalized schema is much faster in performance so you can get a quick response from the database. OLTP database designers follow the Normalization rules but the tables in Data warehousing(OLAP) data bases are in the De normalized form, they won't follow the Normalization technique. For this reason we are using more complex queries in Data warehouses which uses more system resources. Some one might explain you better way......... Thanks Blueberry
Is the process of creating table designs by assigning specific fields or attributes to each table in a database?
Normalization is the process of creating table designs by assigning specific fields or attributes to each table in a database.
What is a data base constraint?
#.In the field of relational database design, normalization is a systematic way of ensuring that a database structure is suitable for general-purpose querying and free of certain undesirable characteristics-insertion, update, and deletion anomalies-that could lead to a loss of data integrity. ... 1.database contraints provide a way to guarantee that;-rows in a table have valid primary or unique key value. 2.-rows in a dependent table have valid foreign key values that reference rows in a parent table. 3.-individual column values are valid
Find out functional dependencies?
A constraint between two sets of attributes is known as functional dependency in relational database. Determination of functional dependencies is vital in database denormalization, normalization and relational model.
Describe database normalization?
Database Normalization is the process of organizing the fields and tables of a relational database to minimize redundancy and dependency
Describe the dependency diagram and explain its purpose?
A dependency diagram is a visual representation of a dependency graph. Dependency diagrams are integral to software development, outlining the complex, interrelationships of various functional elements. Typically in a dependency diagram, arrows point from each module to other modules which they are dependent upon.The dependency diagram is used as an aid to normalization within database design.
How functional dependency is related to database table design?
The functional dependency is related to the database table design through the foreign and primary keys. The foreign and primary keys are functionally dependent on each other.
Difference between partial dependency and fully functional dependency?
The difference is that partial dependency is when a database's attribute is only partially dependent on the primary key. Fully functional dependency is when the attribute is entirely dependent on the key.
What do you understand by Normalization?
Normalization is the process of organizing data in a database to reduce redundancy and dependency by dividing larger tables into smaller ones and defining relationships between them. It ensures data integrity and avoids anomalies like update, insert, or delete anomalies. Normalization is essential for efficient database design and maintenance.
What is the purposed normalization in database?
The purpose of normalization is to reduce the chances for anomalies to occur in a database. The Normalization also forces you to use a database in a Object orientated manner. (This is good of course.)
Why normalisation necessary during database design?
Database normalization, or data normalization, is a technique to organize the contents of the tables for transactional databases and data warehouses. Normalization is part of successful database design; without normalization, database systems can be inaccurate, slow, and inefficient, and they might not produce the data you expect.
What is non trivial functional dependency?
-->non trivial functional dependency is totally opposite to the trivial functional dependency. --> non trivial dependency means X-->Y that is if Y is not proper subset of X table or relation with X then it said to be non trivial functional dependency.
Describe the purpose of normalizing data and also list out the dependencies involved in the process of normalization?
The purpose of normalizing data in DBMS is to reduce the data redundancy and increase the consistency of data. a) Partial dependency: non-prime attribute ( field) depends on other non-prime attributes b) Functional dependency c) Transitive dependency
Why 4NF is preferable then bcnf .with example?
Normalization is a process to reduce the redundancy by removing function dependencies BCNF (Boyece code normal form) has all functional dependencies A to B are trivial of discriminator should be superkey. To get relation in BCNF, Splitting the relation schema not neccessarily preserve all functional dependency, Loss less decomposition and dependency are main points for the normalization sometime, it is not possible to get a BCNF decomposition that is dependency, preserving. While 4NF has very similar definition as BCNF. A relational Schema is in 4NF, if all multivalued dependencies A to B are trivial and determinate A is superkey of schema. If a relational schema is in 4nf, it is already in BCNF. and 4NF decomposition preserve the all functional dependency. so 4NF is preferable than to have BCNF.
What is functional dependency in oracle?
In Oracle, functional dependency is when the value of one thing is completely determined by another thing. Functional dependency happens when one attribute determines another attribute in a relation.
