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Explain Two phase locking protocol
A transaction is consider as to follow the two-phase locking protocol if all locking operations precede the first unlock operation in the transaction. Such type of transaction can be divided into two phases: and expanding or growing (first) phase, throughout which new locks on items can be acquired but none can be released; and a shrinking (second) phase, throughout which existing locks can be released but no new locks can be obtained. This two-phase protocol can make sure the serializability because all the data items needed by a transaction will be locked at the starting of the transaction and if other transaction needs to use those data items then it has to wait till they become unlocked.
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.
explain ER Modeling?
Convert the following ER - diagram (Entity Relationship Diagram) into a relational database (the primary keys are underlined): 2160_Convert the following ER - diagram into a
What is meant by object identifiers? Object-oriented systems use an object identifier to recognize objects. Object identifiers are unique: that is every object has a single ide
Let us first look into some of the important features of ER model. Entity relationship model is a high-level conceptual data model. It permits us to define the data invo
Explain the two types of participation constraint. 1. Total: The participation of an entity set E in a relationship set R is said to be total if each entity in E participates i
What is use of generating such tables? How can you create temporary tables? When you require a table only for a short time after that you want it to disappear automatically you
Describe Object Relational model ? Object Relational Model - This model combines the characteristics of both relational model and object oriented model. It extends the tradit
Indexed (Indexed Sequential) File Organisation It organises the file like a big dictionary, i.e., records are kept in order of the key but an index is stored which also allows
Eliminate Repeating Groups The problem is, "Find out the list of employees, who knows DB2". For this problem we require to perform an awkward scan of the list looking for re
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