An outstanding functionality of SQL is its support for automatic_____ to the target data.
Answer: B
Correct answer: navigation
In older network and hierarchical systems the programmer had to navigate to the data record by record. SQL is declarative: the query says what is wanted and the system works out how to reach it, which is what automatic navigation means.
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The collection of information stored in a database at a particular moment is called as ......
Answer: B
Correct answer: instance of the database
An instance is the data present at a particular moment; the schema is the structure, which stays the same while the instance changes with every insert and delete.
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When an E-R diagram is mapped to tables, the representation is redundant for
Answer: B
Correct answer: weak relationship sets
A weak entity is identified by its owner, so the relationship connecting the two carries no information beyond what the weak entity's own table already holds through the borrowed key. Giving that relationship a table of its own would therefore be redundant.
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The statement that is executed automatically by the system as a side effect of the modification of the database is
Answer: D
Correct answer: trigger
A trigger is a piece of code the DBMS runs automatically when a specified modification occurs, which is exactly the description given. An assertion is a condition that must hold but does not itself act.
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The normal form that is not necessarily dependency preserving is
Answer: A
Correct answer: BCNF
A relation can always be decomposed into third normal form while preserving all its functional dependencies, but a BCNF decomposition sometimes cannot: enforcing one of the original dependencies may require a join. That is the price of BCNF's stronger guarantee, and it is why 3NF is often preferred in practice.
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_____is a full form of SQL.
Answer: C
Correct answer: Structured query language
SQL stands for Structured Query Language. It is more than a query language, since it also defines and controls data, but the name records its origin.
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The relational model is based on the concept that data is organized and stored in two-dimensional tables called ______
Answer: C
Correct answer: Relations
The relational model stores data in two-dimensional tables called relations, whose rows are tuples and columns attributes. The name comes from the mathematical relation, a set of tuples over given domains.
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A _____ is used to define overall design of the database
Answer: D
Correct answer: schema
A schema is the definition of the whole database structure - its tables, their columns and the constraints between them. A data definition language is what the schema is written in, which is not the same as the schema itself.
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Which of the following ensures the atomicity of the transaction?
Answer: A
Correct answer: Transaction management component of DBMS
Atomicity - all of a transaction's effects or none - is enforced by the transaction manager, which decides when to commit and calls for undo when a transaction aborts. Concurrency control provides isolation, a different one of the ACID properties.
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The default level of consistency in SQL is
Answer: D
Correct answer: serializable
The SQL standard's default isolation level is serializable, the strictest, in which concurrent execution must be equivalent to running the transactions one after another. Individual products often default to something weaker for performance, but the standard's default is this.
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