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what is view in sql how is it definedany relation that is not part of the logical model but is made visible to a user as a virtual relation is known
what is the use of sub queriesa sub query is a select-from-where expression that is nested with in another query a common use of sub queries is to do
what is the use of group by clausegroup by clause is used to be relevant aggregate functions to a set of tuples the attributes given in the group by
what are aggregate functions and list the aggregate functions supported by sqlaggregate functions are functions that take a collection of values as
what is the use of union and intersection operationunion the result of this operation contains all tuples that are either in r1 or in r2 or in both
list the set operations of sql1 union2 intersect operation3 the except
list the string operations supported by sql1 pattern matching operation2 concatenation3 extracting character strings4 converting among uppercase and
define tuple variabletuple variables are used for comparing two tuples in the same relation the tuple variables are explained in the from clause by
what is the use of rename operationrename operation is used to rename both relations and an attributesit uses the as clause taking the formold-name
give the general form of sql queryselect a1 a2 anfrom r1 r2 rmwhere
what are the three classes of sql expressionsql expression consists of three
what are the categories of sql commandsql commands are separated in to the following categories1 data - definitition language2 data manipulation
what are the parts of sql languagethe sql language has various partsdata - definitition language data manipulation language view
what is foreign keya relation schema r1 derived from an er schema may contain among its attributes the primary key of another relation schema r2this
write short notes on schema diagrama database schema along with primary key and foreign key dependencies can be depicted pictorially by schema
write short notes on domain relational calculusthe domain relational calculus uses domain variables that take on values from an attribute domain
write short notes on tuple relational calculusthe tuple relational calculation is anon procedural query language it defines the desired information
what is a project operationthe project operation is a unary operation that returns its argument relation with particular attributes left out
what is a select operationthe select operation selects tuples that please a given predicate we use the lowercase letter sigma to denote
define- relational algebrathe relational algebra is a procedural query language it having of a set of operations that take one or two relation as
what is a super keya super key is a set of one or more attributes that collectively permits us to recognize uniquely an entity in the entity
what is a primary keyprimary key is chosen by the database designer as the principal means of identifying an entity in the entity
what is a candidate keyminimal super keys are known as candidate
define the term domainfor each n every attribute there is a set of permitted values known as the domain of that
define tuple variabletuple variable is a type of variable whose domain is the set of all