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Illustrate the statement 'Projection operation distributes over the union operation'. Give an example.
Ans: ΠL(E1 ∪ E2) = (ΠL(E1)) ∪ (ΠL(E2))
This says that result acquired by projecting on an attribute set A, after taking union of two relations is similar as union of two relations each of which is a projection of original relations on A.
Waterfall model is the linear model. The process is completed by step by step. We couldn't stop in between of the process. Prototype model: after get the model by low cost budget o
E-R model uses this symbol to represent weak entity set ? A Doubly outlined rectangle symbol is used to represent weak entity set.
The indices are accumulated in the index files. The data is accumulated in the data files. Indices give fast access to data items. For example, a book database may be managed in th
Explain What is Relation? A database relation is a predefined row or column format for storing information in a relational database. Relations are equal to tables.
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Explain four causes for failures in data warehouse projects
Write a Query that uses the UNION Operator 1. Use the Software Experts database to: a. Display the first and the last name of all consultants who worked on any projects f
Define Join and Outer Join and differentiate between them. Ans: Join - It generates all the combinations of tuples from two relations which satisfy a join condition. Oute
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