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# Database management systems DBMS TRUE or FALSE questions with answers explained for competitive and entrance exams.

## TRUE or FALSE questions in DBMS

1. Once the database engine translates a SQL query to a relational algebra logical query plan, that choice determines how the physical query will be executed.
(a) TRUE                                          (b) FALSE

 Answer: FALSE There are usually several possible physical query plans for a given logical plan

2. The relational schema produced as result of applying ER model is always in first normal form.
(a) TRUE                                          (b) FALSE

 Answer: FALSE In ER model, there are rules to convert or reduce every component in an ER diagram. Application of ER model in designing the database always resulted in relations that are at least in 1NF always. Also, some of the relations in the resulting database may even be in 3NF or BCNF.

3. Following schedule is conflict serializable.
r1(A); r2(B); r1(B); w2(B); w1(A); w1(B); r2(A); w2(A); c1; c2.
(a) TRUE                                          (b) FALSE

 Answer: FALSE The given schedule has formed a cycle in the precedence graph. Hence, it is not conflict serializable. The conflicting instructions that result in edges between transactions T1 and T2 are highlighted with links for your understanding purpose.

4. Following schedule is conflict serializable.
r1(A); r2(B); r3(A); r2(A); r3(C); r1(B); r3(B); r1(C); r2(C); c1; c2; c3.
(a) TRUE                                          (b) FALSE

 Answer: TRUE The given schedule does not have conflicting instructions. Instead it is full of read only transactions. Hence, it is conflict serializable.

5.  Suppose relations R1 and R2 currently have n1 and n2 tuples respectively. Then their Cartesian product R1 X R2 can have at most n1 X n2 tuples, but will typically have less than n1 X n2 tuples.
(a) TRUE                                          (b) FALSE

 Answer: FALSE Cartesian product is a cross product. Performing Cartesian product operation between any two relations will strictly result in the temporary relation that consists of n1 X n2. If suppose it results in less than n1 X n2 tuples that means it executed with some select operation (filtering conditions).

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