Oracle SQL Oracle SQL SELECT Statements

Question 1

Which clause is used to filter rows AFTER grouping in Oracle SQL?

Accepted Answer

HAVING

Answer

The HAVING clause filters rows after the GROUP BY aggregation is applied, unlike WHERE which filters before grouping.

Question 2

What does SELECT DISTINCT do in Oracle SQL?

Accepted Answer

Removes duplicate rows from the result set

Answer

SELECT DISTINCT eliminates duplicate rows from the query result, returning only unique combinations of the selected columns.

Question 3

Which Oracle SQL keyword limits the number of rows returned using a row-limiting clause (Oracle 12c+)?

Accepted Answer

FETCH FIRST

Answer

Oracle 12c introduced the FETCH FIRST n ROWS ONLY syntax as the standard row-limiting clause.

Question 4

What is the purpose of the ORDER BY clause in a SELECT statement?

Accepted Answer

Sorts the result set by one or more columns

Answer

ORDER BY sorts the final result set in ascending (ASC) or descending (DESC) order based on specified columns.

Question 5

In Oracle SQL, which pseudo-column assigns a sequential number to each row in a result set before ORDER BY is applied?

Accepted Answer

ROWNUM

Answer

ROWNUM is a pseudo-column assigned by Oracle before sorting, so filtering with ROWNUM must be done in a subquery to work correctly with ORDER BY.

Oracle SQL Practice Test