Suppose there are two relations: R1 and R2. If C1 and C2 are the selection conditions, and A1 and A2 are the attributes of the relation R1, then which of the given query transformations are correct?

1. 0C1 (0C1 (R1)) -> 0C2 (0C2 (R1))

2. 0C1 (nA1 (R1)) -> nAl (0C1 (R1))

3. 0C1 (R1 U R2) -> 0C1 (R1) U 0C1 (R2)

Which database security mechanisms is used to enforce multilevel security by classifying users and data into various security levels? 1. Mandatory security mechanisms 2. Discretionary security mechanisms

Which of the given options is targeted and focused on a single subset of an organization?

Consider a table named 'Account,' having the following fields.

Which of the following relational algebra expressions represents the query that will f‌ind names of customers having an account balance of over Rs. 5.000?

In which areas data-mining technology can be applied? 1. Marketing 2. Finance 3. Manufacturing 4. Healthcare

The hash address space in static hashing is not always the same.

A database system without concurrency control may cause:

Concurrency control is used .

What is the order of execution of operations during a pessimistic concurrency control technique?

Which of the following indexes in databases is usually dense?