CS Database Management & SQL 5

Question 1

Which SQL statement modifies existing rows in a table?

Accepted Answer

UPDATE

Answer

UPDATE changes column values in existing rows, while ALTER changes the table structure.

Question 2

What is a transitive dependency, which third normal form (3NF) eliminates?

Accepted Answer

A non-key attribute depending on another non-key attribute

Answer

3NF requires non-key attributes to depend only on the key, not on other non-key attributes.

Question 3

Which SQL pattern matches any last name starting with 'Mc'?

Accepted Answer

WHERE last_name LIKE 'Mc%'

Answer

The % wildcard matches any sequence of characters following the literal 'Mc'.

Question 4

Two transactions each hold a lock the other needs and neither can proceed. This situation is called:

Accepted Answer

Deadlock

Answer

A deadlock is a circular wait where transactions block each other indefinitely until one is aborted.

Question 5

Which command removes all rows from a table quickly without logging individual row deletions in most systems?

Accepted Answer

TRUNCATE TABLE

Answer

TRUNCATE deallocates data pages rather than deleting rows one by one, making it faster than DELETE.

(CS) Computer Science Practice Test