functional dependency in dbms

hi students coming to the next topic in the subject database management system is functional dependency so this is one of the important concept that you have to know it is a dependency relationship between the relay attributes that are present in the relation so if you know what is a functional dependency then it is easy for you to understand the different normal forms that are used in thee for creating the tables ok now let us see what is is a functional dependency a functional dependency is nothing but it is a relationship it is a relationship that exists when one attribute uniquely determines another attribute that you call it as a functional dependency so means it a nursing in a table okay so in a table a functional dependencies is nothing but it explains the relationship that exists when one attribute one attribute uniquely determines the another attribute so this uniquely determines uniquely determines the another attribute means it is a dependency relation is there between these two attributes attributes or nothing but the fields that are present in the table okay so let us take if R is a relation relation is nothing but a table so this is an R R is a relation so a table with attributes with attributes x and y so x and y so here a functional dependency between these two attributes is represented as X points to Y which specifies Y is functionally dependent on X means this Y attribute this Y attribute depends on X attribute that you say Y is functionally dependent on X Y this Y is dependent on X because X is always here uniquely determines determines the Y value so this is a functional dependence it means one attributes is depends upon the another attribute so let me take one more it is a set of constraints between two attributes in a relation we said it is a set of constraints between two attributes in a relation so you can also say that functional dependency is nothing but it is a set of constraints means some rules between two attributes in a relation that is this is the X attribute and this is the Y attribute so Y is functionally dependent on functionally dependent on X attribute so here this X is always determinant it determines the another attribute so you call this X is a determined means it is nothing but it is an identification key you also call this as an identification key identification key can be uniquely determines so that's why we are saying it is a relationship that exists when one attribute that is X attribute uniquely determines the another attribute so whenever we say it is a uniquely determines uniquely determines is nothing but it is having some identification key okay so this whatever the attributes that values that are present in the Y those Y values will depends on the X values that is a functional dependency so it's always determinant and Y is always dependent so here the right hand side is always depends upon the left hands okay let me take one example to explain about this functional dependency example so if every attribute suppose B of our if every attribute B of our our is relation means the table name so in the table a B is one attribute this B attribute depend dependent of a then attribute a is a primary key primary key is nothing but it is a uniquely it is this an identification key which is uniquely determined so R is a relation here a and B your attributes so this attribute a is represented as a primary key means this is uniquely determined uniquely determines so that's why B always depends upon a if B depends upon a then a functional dependencies exist between these two attributes B functionally dependent on a so suppose let us take example ID name and surname so here the ID suppose we have taken as s1 name bhajana and initial is ps2 identification number Priya this is G s3 and again the name is Bonham this is M okay so here this ID is nothing but it is a primary key it is an identification key why I am calling this as an identification key because this is uniquely identified with the help of this key we can identify the we can retrieve the values of the non-key attributes so this should be unique s1 is to s33 different values okay so here you will get dependency relation between this attributes or ID name means name is functionally dependent name is depend on ID so with the help of ID we can retrieve the value of the name and the surname of a that particular person okay so that's why name is functionally dependent on ID so here the name determines the values of ID in the same way IIT tends to surname so this surname is functionally dependent on ID so then you can say this table is in functionally dependent table so these one attributes will be depends upon the another attribute that is a key attribute then you can say it is a functional dependence with attributes a relation that exists between those attributes is functionally dependent I hope you understand what exactly the functional dependencies okay thank you

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Keywords: functional dependency in dbms with example, functional dependency in dbms with example video, functional dependency in dbms with example tutorial, functional dependency in dbms in english, functional dependency example, functional dependency example in dbms, functional dependency example problems, functional dependency database, functional dependency database definition

Id: X3c1phdyjbU

Length: 7min 45sec (465 seconds)

Published: Wed Mar 07 2018