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[Music]
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hello friends welcome back to our
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channel so in today's session we'll
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discuss about
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the notations of er diagram
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so in the previous session we have
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discussed about the ear model so what is
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an er model and what are the components
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of vr model
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so ear model is a
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design phase so that means
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design of a database so in order to
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design that one so we have to use some
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graphical representation diagrammatic
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representation of a database so using
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this graphical representation or a
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diagrammatic representation so we have
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to use
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the symbols for all the components of a
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year model so we will see what are the
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notations to represent the components of
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ear model
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so notations
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of
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er diagram
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er diagram right
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so first let us
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recall the components the components are
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entity attribute and the relationship
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so
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entity
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attribute
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and
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relationship so these are the components
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and we have to draw the ear diagram
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based upon
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these components so in that we know that
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it's a strong entity
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so two categories a strong entity
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and
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weak entity
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so here in the ear diagram the strong
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entity is represented as a
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rectangle box
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rectangle box so this represents the
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strong entity
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this represents the strong negative
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coming to the weak entity
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double rectangle box is represented as a
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weak entity
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so this is represented as a weak entity
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okay so if in our ear diagram if you
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want to represent any weak entity we
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have to draw this
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double rectangle
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coming to the attributes the first one
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key attribute so this key attribute
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so generally the attribute so generally
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the entity is represented as
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this one
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attribute is represented as
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an over
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over right and relationship is
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represented as
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a rhombus or a diamond symbol
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okay now key attribute is represented as
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google
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with
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underline so underlining the
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key
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right
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and
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single attribute or a simple attribute
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simple attribute is a normal ellipse it
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is represented as a normal ellipse
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and multi-valued
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multi-valued attribute is represented as
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double ellipse
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double ellipse is represented as a multi
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value right
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so this is a multi-valued attribute
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and derived attribute so derived
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attribute is represented as a
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dotted ellipse
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dotted ellipse
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right so this is a derived attribute and
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a composite attribute
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so
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i'll write right here
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composite attribute composite attribute
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is represented as
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so extension that means
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again it will be derived as
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different attributes so this this type
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we can consider as a composite attribute
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right so further divided one attribute
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dividing further okay
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next the relationship
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it is represented with a
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diamond or a rhombus so this is for
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relating the strong entity
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strong entity the relation
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for a strong entity
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coming to the weak entity
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so
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double diamond is a
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relation for
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weak entity
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double diamond is a relation for weak
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entity so these are the notation for
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components used in er diagram or er
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model so these are the three components
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entity attribute and relation so entity
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strong entity and weak entity attributes
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the key single multi-value derived and
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composite
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and similarly the relationship so it is
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usually
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represented as a diamond and a normal
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diamond symbol is used to give a
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relation between the strong entities and
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if you want to give a relation between
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the weak entities that will be
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represented as
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this
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double
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rhombus or double diamond
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right so hope you understood this
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notation so by using these notations we
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have to draw the er model or er diagram
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right so in the further sessions we'll
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see
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the diagram the complete er diagram
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okay so let's stop here i hope you
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understood this one and if you are
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having any doubts regarding this one
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feel free to post your doubts in the
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comment section definitely i will try to
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clarify all your doubts if you really
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enjoyed my session like my session share
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thanks for watching thank you very much