1Z0-006 Fundamental Database Concepts 3

Question 1

Which SQL clause filters rows AFTER a GROUP BY aggregation has been performed?

Accepted Answer

HAVING

Answer

HAVING filters groups produced by GROUP BY, whereas WHERE filters individual rows before grouping occurs.

Question 2

What does DCL (Data Control Language) consist of in SQL?

Accepted Answer

GRANT and REVOKE statements

Answer

DCL includes GRANT (to give privileges) and REVOKE (to remove privileges), controlling user access to database objects.

Question 3

Which type of JOIN returns all rows from the left table and matching rows from the right table, with NULLs for non-matching right rows?

Accepted Answer

LEFT OUTER JOIN

Answer

A LEFT OUTER JOIN returns all rows from the left table plus matching rows from the right table; unmatched right-table columns appear as NULL.

Question 4

What is data redundancy in a database, and why is it problematic?

Accepted Answer

Storing the same data in multiple places; it leads to inconsistency and update anomalies

Answer

Data redundancy means the same data is stored in multiple locations, causing update anomalies where changing one copy may leave other copies out of sync.

Question 5

In a relational database, what is a candidate key?

Accepted Answer

Any minimal set of attributes that can uniquely identify a row

Answer

A candidate key is any minimal superkey — a set of attributes that uniquely identifies rows, from which the primary key is chosen.

(1Z0-006) Oracle Database Foundations Associate Practice Test

(1Z0-006) Oracle Database Foundations Associate Practice Test

1Z0-006 Fundamental Database Concepts 3