Oracle Database SQL Practice Test

1. Which SQL statement is used to add a new column to an existing table in Oracle?

ADD COLUMN

ALTER TABLE ... ADD

MODIFY TABLE

INSERT COLUMN

2. What does the HAVING clause filter in Oracle SQL?

Individual rows before grouping

Grouped data after aggregation

Columns in the SELECT list

Table joins before execution

3. In Oracle, which JOIN returns all rows from both tables, matching where possible?

INNER JOIN

LEFT OUTER JOIN

FULL OUTER JOIN

CROSS JOIN

4. Which keyword removes duplicate rows from a query result in Oracle?

DISTINCT

UNIQUE

REMOVE DUPLICATES

GROUP BY

5. What is the purpose of the COMMIT statement in Oracle?

Undo all changes in a transaction

Save changes permanently to the database

Create a savepoint

Lock the table for updates

6. Which Oracle function returns the current system date and time?

GETDATE()

NOW()

SYSDATE

CURRENT_TIMESTAMP()

7. In Oracle, what does a subquery in the WHERE clause typically do?

Filter rows based on a condition derived from another query

Join two tables together

Create a temporary table

Order the result set

8. Which constraint ensures that a column value is unique across all rows in Oracle?

PRIMARY KEY

UNIQUE

NOT NULL

CHECK

9. What does the ROLLBACK statement do in an Oracle transaction?

Saves all pending changes

Undoes all changes since the last COMMIT

Locks the current session

Creates a backup of the table

10. In Oracle SQL, which clause is used to sort query results?

SORT BY

ORDER BY

GROUP BY

ARRANGE BY

11. Which aggregate function returns the highest value in a column?

TOP()

HIGHEST()

MAX()

MAXIMUM()

12. What is the primary purpose of a primary key in an Oracle table?

Speed up data retrieval

Uniquely identify each row

Encrypt sensitive data

Organize rows alphabetically

13. In Oracle, which statement is used to remove all data from a table but keeps its structure?

DELETE FROM table_name

DROP TABLE table_name

TRUNCATE TABLE table_name

REMOVE TABLE table_name

14. Which Oracle function converts a string to uppercase?

UPPER()

UPPERCASE()

CAPS()

CONVERT()

15. What does a correlated subquery in Oracle do differently from a regular subquery?

Executes once and returns multiple rows

References columns from the outer query for each row processed

Must be placed in the FROM clause

Always returns NULL values