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[Music]
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hello friends welcome back to our
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channel
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so in today's session we discuss about
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one more topic in dbms that is a
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relational algebra
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so coming to this relational algebra so
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this is a theoretical language and which
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is a base language for query language
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it is a theoretical language
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theoretical language
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and
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base for
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sql
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base for sql so usually
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the relational model
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relational model
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we discuss about this one so relational
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model means the data will be represented
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in tables right relations in terms of
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relations
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and
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in order to retrieve the data
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in order to retrieve the data it
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requires two different languages one is
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theoretical
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and based upon the theoretical we have
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to implement the practical
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and these theoretical languages are
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relational
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algebra
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and
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relational
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calculus
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and the practical knowledge is nothing
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but the practical
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uh programming language is estimate so
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in the relational model if you want to
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get the data practically we have to
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write down the queries and
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without using this sql we can't get the
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data from the table
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so in order to write the queries first
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we need to have a knowledge on this
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relational algebra
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right so
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this is a procedural language we call
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this relational algebra as a
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procedural language
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procedural
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language
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and
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we give some condition and based upon
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that condition the data will be
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retrieved from the
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table
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and now
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in this session we will discuss about
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the basic interaction of this relational
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algebra and what are the different
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operators available in this relational
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algebra and from the next sessions we'll
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go in deep with the operators different
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operators
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so coming to this one
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there are different operations available
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in relational algebra and here the input
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the input will be the relation
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the input will be the relation and we
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will apply some operators okay
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and the output
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the output will also be in the form of a
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relation itself relation itself so here
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the relation means table
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relation means in the form of table so
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input and outputs will be tables and in
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between we have to apply the operations
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now what are the different operations
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that can be done on this relational
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algebra
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see
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relational algebra
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so different operations first
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unary operations unary
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operators or operations
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set theory operations
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set theory operations
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binary operations
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extended
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or derived
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or derived operations
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so these are all comes under this
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relational algebra so coming to the
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unary operations
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so first one is a selection in order to
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select
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the data from the table so it is
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represented as
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sigma sigma
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and the second one is a projection
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so what exactly we required to display
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in the table right so that will be
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pi
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and rename
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rename
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that's a row row symbol right so rename
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means the name itself indicates we can
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rename the table so all these operations
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will be performed on a single relation
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okay so selection will be applied on
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single relation projection will be
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applied on single relation and similarly
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rename is also applied on symbolization
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so that's why we call these
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operations as a unary operations so that
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means only one relation we are going to
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apply all these things on one relation
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coming to the secondary operations you
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are aware about this theory so union
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operation
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intersection operation
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so union means just combining the all
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from the two tables so here uh the
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section operations are also one type of
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binary operations because here also will
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use the two different relations so we'll
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apply these operations on two different
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relations so union means it will combine
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the data of two tables intersection
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means it will give the
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common elements from two tables
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and
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cross product cross product
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so this is also
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the set theory operation so we'll go one
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by one with an example in the further
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sections right so let me list out all
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the operations that can be performed on
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this relational algebra in this class
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and coming to the binary operations
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so
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join operation
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join operation so it is represented as
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this one
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join operations
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and
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in this join
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particularly inner join
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inner join operation comes under here
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and in the extended we have this outer
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join
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outer joint
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right so inner joint in that inner join
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again
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theta joint
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and
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another one is a natural joint
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natural join and here
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left outer
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join
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right outer join
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full outer join
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full outer join and also
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some aggregate functions there will be
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some aggregate
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aggregate functions
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so that comes under
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that comes under this extended right
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and coming to this one inner join
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and
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division division operation division
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operation with this one and here
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here
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uh we'll be having one more called
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minus
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or ascetic difference
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or
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set difference so which is nothing but
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minus
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right so these are all the operations
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that can be performed performed on a
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relational algebra so unary operations
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set theory operations binary operations
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and extended or derived operations
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so urinary operation selection
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projection training
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uh
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safety the operations union intersection
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corresp cross product and minus
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and here it is uh
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sorry
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see
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join and division operation in in join
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there are two two categories of joints
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in the joint and how to join and here we
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comes under inner join and in that inner
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join again it is it can be implemented
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with the two ways one is a theta join
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another one is a natural join and coming
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to the extender or railroad operations
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the outer join in the outer join there
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are three categories left outer join
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right outer join and full outer join and
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some aggregate functions we come center
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here
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so here once again i am repeating so in
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this relational algebra the input will
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be the relation that means a table and
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the output will be also the relation
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right so unary set theory operations
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binary and extended or derived
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operations so let's stop here in the
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next session we'll start with the unary
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operations of relational algebra
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right so if you are having any doubts
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regarding this one feel free to post
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your doubts in the comment section
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definitely i will try to clarify all
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