ADatabase Administrator (DBA)is responsible for the management, security, and performance of a database system. This includes controlling access to data, ensuring database integrity, optimizing performance, managing backups, and protecting the system from unauthorized access.
Option A (Incorrect):A DBA is not just a consumer of data but is primarily responsible for the database’s management.
Option B (Correct):Security is one of the key responsibilities of a DBA, including enforcing user access controls and implementing encryption and authentication mechanisms.
Option C (Incorrect):While DBAs work with data structures, it is typically the role of adata architectordatabase designerto define data formats and schema structures.
Option D (Incorrect):Developing application programs that interact with the database is typically the role ofsoftware developersordatabase programmers, not DBAs.
[Reference:Database Administration best practices from SE 3050 zyBooks., ]
Question 2
What does the aggregate function do?
Options:
A.
It computes values over a set of rows.
B.
It selects rows that appear in one table but not another.
C.
It eliminates one or more columns of a table.
D.
It lists combinations of rows in two tables.
Answer:
A
Explanation:
Anaggregate functionperforms acalculation over multiple rowsand returns asingle value. Examples includeSUM(), AVG(), MAX(), MIN(), and COUNT()in SQL.
Option A (Correct):Aggregate functions compute values over aset of rows, like summingtotal sales or averaging grades.
Option B (Incorrect):Selecting rows that appear in one table but not another is done usingset operations (EXCEPT or MINUS in SQL).
Option C (Incorrect):Eliminating columns is done using thePROJECToperation orSELECT with specific columns.
Option D (Incorrect):Combining rows from two tables refers to aJOIN operation, not aggregation.
[Reference:Aggregate functions in relational algebra., , , ]
Question 3
Which SELECT statement uses valid syntax for SQL?
Options:
A.
SELECT "column name", "column name" FROM "table name" WHERE "column name"
B.
SELECT column1, column2 WHERE condition FROM table_name;
C.
SELECT ALL column1, column2 FROM table_name;
D.
SELECT column1, column2 FROM table_name;
Answer:
D
Explanation:
Avalid SELECT statementin SQL follows this basic syntax:
sql
SELECT column1, column2
FROM table_name
WHERE condition;
The correct optionDfollows this syntaxcorrectly.
Why Other Options Are Incorrect:
Option A (Incorrect):SQL does not usedouble quotes(") around column/table names unless explicitly required in some databases.
Option B (Incorrect):The WHERE clausemust appear after the FROM clause.
Option C (Incorrect):ALL isnota valid keyword in standard SQL queries.