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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)
Databases and data warehouses both are databases and both contains number of rows and columns of tables containing data. Data warehouse is really different from databases because d
Heap files (unordered file) Mostly these files are unordered files. It is the easiest and most basic type. These files having of randomly ordered records. The records will have
Although, the essential features of E-R diagrams are enough to design many database situations. Though, with more difficult relations and advanced database applications, it is need
What are the aggregate objects in the data dictionary? Views Match codes Lock objects.
What is OOM? Object oriented modeling is an approach by which modeling of systems is done by visualizing the system based on real world concepts. Object oriented modeling does
Can we delete data element, which is being used by table fields. No we cant delete data element.
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
WHAT IS DSS? WRITE ITS REQUIREMENTS.
What are the storage types? The storage types are: a) Volatile storage b) Nonvolatile storage
Critically evaluate the bulleted list of information-related items in this case study. How are each contradictory to the notion of being an information-literate knowledge worker?
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