For each of the following statements, indicate whether it is true or false.

1) In ER, a relationship type can have no key.

2) In SQL, using the command AS will change the database.

3) Any relation in BCNF is also in 2NF.

4) A primary key must consist of only one attribute.

5) A lossless and dependency-preserving decomposition into 3NF is not always possible.

6) Both using OS file system to manage disk space and keeping track of free blocks can improve disk access.

7) SQL cannot control sequences of database operations.

8) Frequent checkpoints can reduce the amount of data lost if a disk is destroyed.

9) The time-stamp ordering method never produces deadlocks.

10) As a concurrency control method, optimistic control is a good option if there is a lot of interaction between transactions.

 

1)true

2)false

3)true

4)false

5)false

6)true

7)false

8)true

9)true

10)false

Step-by-step explanation

1)it is not necessary in a relationship in er model that it should have a key.relationship is between attributes .

2)AS command is used to rename the column .

3)It is a must condition for BCNF that it should be in 2NF.

4)A primary key is a set of minimal attributes that is uniquely identified. It can be more than one.

5)it is always possible in 3NF but not possible in BCNF.

6)If we will keep track of free blocks and manage disk space then it can improve disk access.

7) SQL can control sequences in database.

8)Frequent checkpoints will clear the old log files and thus data lost will be minimal.

9)time stamp method prioritizes transactions .The priority of the older transaction is higher that's why it executes first. TS protocol ensures freedom from deadlock that means no transaction ever waits.

10)No in optimistic control method there should be no interference of transactions therefore it is false.