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What is data model? Explain object based and record based data models?
Ans: A data model is an abstract model in which describes how data is represented and accessed.
(i) Object based data models: Same to a relational database model, but objects, classes and inheritance are directly supported within database schemas and in the query language
(ii) Record based data models: is a database model based on first-order predicate logic. Its core idea is to elaborate a database as a collection of predicates over a finite set of predicate variables, describing constraints on the possible values and combinations of values.
Attributes that are directly kept in the data base. For example, 'Birth date' attribute of a person. Derived Attributes that are not stored directly but can be derived
What is the use of keyword ISA? The use of keyword ISA is to show that a class is a specialization of another class.
Consider the following database schema: STAFF(StaffNo, fName, lName, Position, sex, dob, branchNo) BRANCH(BranchNo, Street, City) Assume the following for the above database
Hardware failure : Hardware failures are the failures when some disk or hardware chip fails. This may result in loss of data. One such trouble can be that a disk gets damaged and
The data of a view is not physically stored, but derived from one or more tables. True the data of a view is not physically stored
Write short notes on relational constraints? Relational Constraints are: 1. NOT NULL 2. Unique 3. Primary key 4. Foreign key 5. Table check
This constraint shows that the key attribute value in each tuple must be unique, i.e., no two tuples have the similar value for the key attribute. This is because the value of the
Define Timestamp ordering Ans In timestamp-based method, a serial order is made among the concurrent transaction by assigning to every transaction a unique nondecreasing number
Explain the differences between structured data and unstructured data. Structured data are facts concerning objects and events. The most significant structured data are numeric
Implementing software control To implement software control designer must redesign strategy of state event model which is present in dynamic model. There are three basic ap
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