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Define the five basic operators of relational algebra?
Five basic operators of relational algebra are:1. Union (∪∪∪∪) - Selects tuples which are in either P or Q or in both of them. The duplicate tuples are eliminated.R = P ∪ Q2. Minus (-) - Removes generally common tuples from the first relation.R = P - Q3. Cartesian Product or Cross Product (××××) - The cartesian product of two relations is the concatenation of tuples belonging to the two relations and consisting of all probable combination of the tuples.R = P × Q 4. Projection (ππππ) - The projection of a relation is described as a projection of all its tuples over a few set of attributes, i.e., it yields a vertical subset of the relation. It is used to either decrease the number of attributes (degree) in the resultant relation or to reorder attributes. The projection of a relation T on the attribute A is denoted through πA(T).5. Selection (σσσσ) - Selects only some of the tuples, those satisfy given criteria, from the relation. It yields a horizontal subset of a given relation, i.e., the action is defined over a complete set of attribute names but just a subset of the tuples are involved in the result.R = σB(P)
Name the various privileges in SQL? A) Delete B) Select C) Insert D) Update
Aggregation : One limitation of the E-R diagram is that they do not permit representation of relationships between relationships. In such a case the relationship along with its ent
Explain the Log Based Recovery Method? The system log that is generally written on stable storage consists of the redundant data required to recover from volatile storage failu
What is data integrity? Ans: It is the data consisted of in database that is accurate and consistent. (Data integrity means that the data should be valid as per to the give
Describe the host language? Host Language: You could write applications along with SQL statements embedded inside a host language. The SQL statements give the database inter
What is the use of rename operation? Rename operation is used to rename both relations and an attributes. It uses the as clause, taking the form: Old-name as new-name.
Find the names of all Albums that have more than 30 tracks. Result: (name: varchar(255))
Consider the following frequency counts of some itemsets in a transaction database r : freq({A}, r) = 0.405 freq({B}, r) = 0.510 freq({C}, r) = 0.303 freq({A
Creating views with check option : This option limits those updates of data values that cause records to go off the view. The following instance tells this in more detail: Examp
Although how will the system recover The selection of REDO or UNDO for a transaction for the recovery is completed on the basis of the state of the transactions. This state is
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