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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.
Explain entity integrity and referential integrity rules within relational model. Show how these are realized in SQL? Entity Integrity Rule - No primary key value could be nu
The Concurrent Transactions Almost every commercial DBMS support multi-user environment. Therefore, allowing multiple transactions to proceed concurrently. The DBMS must make
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Cardinality shows the number of instances of an entity associated with another entity participating in a relationship. Depend on the cardinality binary relationship can be further
Consider the following six relation schemes and their corresponding sets of functional dependencies. In each case identify a. All the candidate keys b. The highest normal for
Define an operator that a Relational Algebra does not have Ans: Relational Algebra does not have Aggregation operators.
What is nested relational model? The nested relational model is an extension of relational model in which domains might be either atomic or relation valued.
This assignment concerns the Research database. The database ER model is shown above, where attributes are omitted for clarity. The relational model for the database is: Departm
What's the difference between a primary key and a unique key? Both primary key and unique key enforces uniqueness of the column on which they are explained. But by default prim
write an SQL statement to create the database in MYSQL server
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