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What is recursive closure? Why is it not possible to describe this operation in relational algebra?
Recursive closure is applied to recursive relationship. An instance of recursive operation is to retrieve all SUPERVISEES of an Employee e at all levels- which is , all EMPLOYEE e directly supervised through e; all employees e" directly supervised through each employee e" and so on .
What is the difference among a primary index and a secondary index? Primary Index: A primary index is an ordered file whose records are of fixed length along with two fields.
Have a look around the site, and at some of the sites they have featured. These are all examples of bad design, and also offer an explanation about why they fall into this category
Give an example of multiple inheritance. One example of multiple inheritance is a committee for students affair which include faculty and administrative staff member.
Describe the types of attributes? Types of attributes: An attribute's category determines the type of values that are permitted in the attribute. For instance, the value vers
what is lossless & dependency preserving decomposition ?
Security: In a centralised system, access to the data can be simply controlled. Though, in a distributed DBMS not only does access to replicated data have to be controlled in many
read-set(T) : Each data items that are read by a transaction T Timestamps : for all transaction T, the start-time and the end time are reserved for all the three phases.
Group By clauses • It is used to group database tuples on the basis of definite common attribute value like as employees of a department. WHERE clause still can be used
Type of database technology
E-R model uses this symbol to represent weak entity set ? A Doubly outlined rectangle symbol is used to represent weak entity set.
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