DBtest

In the 'Serializable' isolation level, when two transactions, T1 and T2, try to insert a new row with the same unique key, what will happen upon commit?

• Both inserts will be successful.

• The database will merge both inserts.

• The second transaction to commit will fail.

• Both transactions will be rolled back.

How can you assign a role the ability to create databases in PostgreSQL?

• By setting the role as a superuser.

• By making the role a member of the db_owner group.

• By granting the role the CREATE privilege.

• By granting the role the CREATEDB privilege.

What is the output of the following SQL query? SELECT membercost, sum(guestcost) AS guest_sum FROM cdюfacilities GROUP BY membercost HAVING membercost > 0

• It returns an error because the GROUP BY clause is missing.

• It returns the sum of quest costs for each facility.

• It returns the member costs for each facility.

• It returns the total quest cost for all facilities.

Consider two tables: Citizens and Passports. Each citizen can have only one passport, and each passport belongs to one citizen. What relationship is this?

• One-to-One

• Many-to-One

• Many-to-Many

• One-to-Many

In a self-join, a table is joined with ...?

• Its parent table.

• its child table.

• Another table with the same structure.

• Itself.

What type of index is created by the following SQL statement? CREATE INDEX idx name ON Employees (Name);

• Unique Index.

• Composite Index.

• B-Tree Index.

• Hash Index.

What is the primary benefit of using the EXPLAIN command before running a complex query?

• a. It provides insight into how the query will be executed by the database engine.

• b. It automatically optimizes the query for better performance.

• c. It creates necessary indexes for the query.

• d. It modifies the query to run faster.

Can a subblock in PL/pgSQL contain other subblocks within it?

• a. Yes, but only one level of nesting is allowed.

• b. No, subblocks cannot be nested.

• c. Nesting subblocks is possible but not recommended.

• d. Yes, subblocks can be nested to any level.

What is an index on expression

• a. An index created on a function or expression involving one or more columns.

• b. An index that is only applicable to text-based columns.

• c. An index created on a standard column without modifications.

• d. An index created on the result of a mathematical expression.

What is the primary purpose of an INOUT parameter in a stored procedure?

• a. Input only

• b. Output only

• c. Neither input nor output

• d. Both input and output