Decomposition means dividing a relation R into {R1, R2, ......Rn}. It is dependency preserving and lossless.Dependency preserving decompositionLet R is decomposed into {R1, R2, ...., Rn} with projected FD set {F1, F2, ......Fn}. This decomposition is dependency preserving if F+ ={F1 U F2 U.........Fn}+.ExampleLet the relation R{A, B, C, D, ... Read More

Decomposition is said to be lossy, if it is impossible to reconstruct the original table from the decomposed tables without loss of information.Decomposition is said to be lossless, if it is possible to reconstruct the original table by using a natural join without any loss of information.AlgorithmGiven below is an ... Read More

Canonical cover is called minimal cover which is called the minimum set of FDs. A set of FD FC is called canonical cover of F if each FD in FC is a Simple FD, Left reduced FD and Non-redundant FD.Simple FD − X->Y is a simple FD if Y is ... Read More

A minimal cover of a set of functional dependencies (FD) E is a minimal set of dependencies F that is equivalent to E.The formal definition is: A set of FD F to be minimal if it satisfies the following conditions −Every dependency in F has a single attribute for its ... Read More

Closure of an attribute x is the set of all attributes that are functional dependencies on X with respect to F. It is denoted by X+ which means what X can determine.AlgorithmLet’s see the algorithm to compute X+Step 1 − X+ =XStep 2 − repeat until X+ does not changeFor ... Read More

Functional dependencies are the constraints that are derived from the meaning and interrelationship of the data. Let F is a set of all functional dependencies. The set of all dependencies that include F as well as all dependencies that can be inferred from F is called CLOSURE of F denoted ... Read More

The overall design of the Database Management System (DBMS) depends on its architecture. A large amount of data on web servers, Personal Computers (PC) and other elements are linked with networks with the help of basic client or server architecture.PCs and workstations are part of Client architecture that are connected ... Read More

The overall design of the Database Management System (DBMS) depends on its architecture. A large amount of data on web servers, Personal Computers (PC) and other elements are linked with networks with the help of basic client or server architecture.PCs and workstations are part of Client architecture that are connected ... Read More

Let’s see the definitions of file systems and database management systems before understanding the difference.File Management SystemIt is nothing but a collection of programs which manage and store data in files and folders in a computer hard disk.It helps in reading and writing data to the hard disk. It is ... Read More

SQL is a Structured Query Language which is the standard and most widely used programming language for relational databases. It is used to manage and organize data in all sorts of systems where all varieties of data relationships exist.Structured Query Language (SQL) ClausesThe SQL clauses are of three types as ... Read More