Test Your Oracle SQL Execution Order Knowledge with This Quiz

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True / False

In Oracle, the SELECT clause is the first clause executed in a SQL query.

True False

The FROM clause is actually executed first, as it identifies the source tables for the query.

True / False

The WHERE clause in Oracle is used to filter rows before any grouping occurs.

True False

The WHERE clause filters rows before they are grouped by the GROUP BY clause.

True / False

In Oracle, the ORDER BY clause is executed last in a SQL query.

True False

The ORDER BY clause is executed last, as it sorts the final result set.

True / False

The GROUP BY clause in Oracle is executed after the WHERE clause but before the SELECT clause.

True False

The GROUP BY clause is executed after the WHERE clause and before the SELECT clause to group the filtered rows.

True / False

In Oracle, the HAVING clause is used to filter groups after the GROUP BY clause is executed.

True False

The HAVING clause filters groups after they have been created by the GROUP BY clause.

True / False

The FROM clause in Oracle is executed after the SELECT clause.

True False

The FROM clause is executed before the SELECT clause to determine the source of the data.

True / False

In Oracle, subqueries in the FROM clause are executed after the main query's WHERE clause.

True False

Subqueries in the FROM clause are executed before the main query's WHERE clause as they provide data for the main query.

True / False

In Oracle, the JOIN operations are performed after the FROM clause but before the WHERE clause.

True False

JOIN operations are part of the FROM clause and are executed before the WHERE clause.

True / False

In Oracle, the DISTINCT keyword is applied after the SELECT clause has retrieved all rows.

True False

The DISTINCT keyword is applied to the result set of the SELECT clause to remove duplicate rows.

Q10

True / False

The Oracle Certified Professional (OCP) exam includes knowledge on understanding the correct SQL execution order, which helps in writing optimized and accurate SQL queries.

True False

The OCP certification covers advanced topics, including the correct execution order of SQL clauses, which is crucial for writing efficient and correct SQL queries.

Q11

Single Choice

In Oracle SQL, which clause is executed first in the SQL execution order?

SELECT WHERE FROMORDER BY

The FROM clause is executed first in the SQL execution order because it identifies the tables involved in the query.

Q12

Single Choice

What is the correct order of execution in a basic SQL query?

FROM, WHERE, SELECT, ORDER BY SELECT, FROM, WHERE, ORDER BY WHERE, FROM, SELECT, ORDER BYSELECT, WHERE, FROM, ORDER BY

The typical SQL execution order is FROM, WHERE, SELECT, and then ORDER BY.

Q13

Single Choice

Which clause is executed last in a SQL query?

WHERE FROM ORDER BYSELECT

The ORDER BY clause is executed last in the SQL execution order as it sorts the result set.

Q14

Single Choice

Consider the following Oracle SQL query:Which clause filters the rows before they are sorted?

SQL Code

SELECT employee_id, department_id
FROM employees
WHERE salary > 5000
ORDER BY employee_id;

SELECT FROM WHEREORDER BY

The WHERE clause filters the rows before they are passed to the ORDER BY clause for sorting.

Q15

Single Choice

In Oracle SQL, which of the following clauses can affect the order of rows in the final output but is not responsible for filtering rows?

FROM WHERE SELECTORDER BY

The ORDER BY clause controls the order of the rows in the output but does not filter rows.

Q16

Single Choice

Given the Oracle SQL query:Which clause is executed right after the GROUP BY?

SQL Code

SELECT department_id, SUM(salary)
FROM employees
GROUP BY department_id
HAVING SUM(salary) > 100000;

SELECT FROM WHEREHAVING

The HAVING clause is executed after the GROUP BY clause to filter groups based on aggregate functions.

Q17

Single Choice

What will be the result of the following Oracle SQL query in terms of execution order?

SQL Code

SELECT employee_id, COUNT(*)
FROM employees
WHERE department_id = 10
GROUP BY employee_id
ORDER BY COUNT(*) DESC;

The query first groups rows, then filters them by department_id, and finally orders them by count in descending order. The query first filters rows by department_id, then groups them by employee_id, and finally orders them by count in descending order. The query first orders rows by count, then groups them by employee_id, and finally filters them by department_id.The query first orders rows by employee_id, then filters them by department_id, and finally groups them by count.

The SQL execution order in this query starts with the WHERE clause (filtering by department_id), followed by GROUP BY, and finally the ORDER BY.

Q18

Single Choice

Consider the following Oracle SQL query:Which of the following steps occurs first during execution?

Summing salaries by department Filtering employees hired after January 1, 2020 Grouping rows by department_idOrdering results by department_id

The WHERE clause filters the rows before they are grouped by department_id and summed.

Q19

Single Choice

In Oracle SQL, when is the SELECT clause executed in the context of the overall query execution order?

Before the FROM clause After the GROUP BY and HAVING clauses Before the WHERE clauseAfter the ORDER BY clause

The SELECT clause is executed after the GROUP BY and HAVING clauses as it defines which columns and expressions to include in the result set.

Q20

Single Choice

What is the execution order of the following Oracle SQL query?

SQL Code

SELECT department_id, AVG(salary)
FROM employees
WHERE job_id = 'IT_PROG'
GROUP BY department_id
HAVING AVG(salary) > 5000
ORDER BY AVG(salary) DESC;

FROM, WHERE, GROUP BY, HAVING, SELECT, ORDER BY WHERE, FROM, GROUP BY, SELECT, HAVING, ORDER BY SELECT, FROM, WHERE, GROUP BY, ORDER BY, HAVINGFROM, WHERE, SELECT, GROUP BY, HAVING, ORDER BY

The correct execution order is FROM, WHERE, GROUP BY, HAVING, SELECT, and finally ORDER BY, which reflects the logical sequence in which the query is processed.

Q21

Multiple Choice

Which SQL code snippet correctly follows the SQL execution order for filtering data before selecting specific columns?

SQL Code

SELECT first_name, last_name
FROM employees
WHERE department_id = 10
ORDER BY last_name;

SELECT first_name, last_name FROM employees WHERE department_id = 10 ORDER BY last_name; SELECT first_name, last_name FROM employees WHERE department_id = 10 ORDER BY last_name; SELECT first_name, last_name FROM employees WHERE department_id = 10 ORDER BY last_name;SELECT first_name, last_name WHERE department_id = 10 FROM employees ORDER BY last_name;

The correct execution order is FROM -> WHERE -> SELECT -> ORDER BY. Options A, B, and C follow this order correctly, while option D incorrectly places SELECT before WHERE.

Q22

Multiple Choice

Which SQL code snippet correctly follows the SQL execution order for applying aggregate functions after grouping data?

SQL Code

SELECT department_id, COUNT(*) AS num_employees
FROM employees
GROUP BY department_id
HAVING COUNT(*) > 5
ORDER BY department_id;

SELECT department_id, COUNT(*) AS num_employees FROM employees GROUP BY department_id HAVING COUNT(*) > 5 ORDER BY department_id; SELECT department_id, COUNT(*) AS num_employees FROM employees GROUP BY department_id HAVING COUNT(*) > 5 ORDER BY department_id; SELECT department_id, COUNT(*) AS num_employees FROM employees GROUP BY department_id HAVING COUNT(*) > 5 ORDER BY department_id;SELECT department_id, COUNT(*) AS num_employees HAVING COUNT(*) > 5 FROM employees GROUP BY department_id ORDER BY department_id;

The correct execution order is FROM -> GROUP BY -> HAVING -> SELECT -> ORDER BY. Options A, B, and C follow this order correctly, while option D incorrectly places SELECT before GROUP BY.

Q23

Multiple Choice

Which SQL code snippet correctly follows the SQL execution order for combining results from two queries?

SQL Code

SELECT employee_id, first_name
FROM employees
WHERE department_id = 10
UNION ALL
SELECT employee_id, first_name
FROM employees
WHERE department_id = 20
ORDER BY first_name;

SELECT employee_id, first_name FROM employees WHERE department_id = 10 UNION ALL SELECT employee_id, first_name FROM employees WHERE department_id = 20 ORDER BY first_name; SELECT employee_id, first_name FROM employees WHERE department_id = 10 UNION ALL SELECT employee_id, first_name FROM employees WHERE department_id = 20 ORDER BY first_name; SELECT employee_id, first_name FROM employees WHERE department_id = 10 UNION ALL SELECT employee_id, first_name FROM employees WHERE department_id = 20 ORDER BY first_name;ORDER BY first_name SELECT employee_id, first_name FROM employees WHERE department_id = 10 UNION ALL SELECT employee_id, first_name FROM employees WHERE department_id = 20;

The correct execution order is FROM -> WHERE -> SELECT -> UNION ALL -> ORDER BY. Options A, B, and C follow this order correctly, while option D incorrectly places ORDER BY before UNION ALL.

Q24

Multiple Choice

Which SQL code snippet correctly follows the SQL execution order for performing a join operation before filtering data?

SQL Code

SELECT e.employee_id, e.first_name, d.department_name
FROM employees e
JOIN departments d ON e.department_id = d.department_id
WHERE e.salary > 5000
ORDER BY e.first_name;

SELECT e.employee_id, e.first_name, d.department_name FROM employees e JOIN departments d ON e.department_id = d.department_id WHERE e.salary > 5000 ORDER BY e.first_name; SELECT e.employee_id, e.first_name, d.department_name FROM employees e JOIN departments d ON e.department_id = d.department_id WHERE e.salary > 5000 ORDER BY e.first_name; SELECT e.employee_id, e.first_name, d.department_name FROM employees e JOIN departments d ON e.department_id = d.department_id WHERE e.salary > 5000 ORDER BY e.first_name;SELECT e.employee_id, e.first_name, d.department_name WHERE e.salary > 5000 JOIN departments d ON e.department_id = d.department_id FROM employees e ORDER BY e.first_name;

The correct execution order is FROM -> JOIN -> WHERE -> SELECT -> ORDER BY. Options A, B, and C follow this order correctly, while option D incorrectly places WHERE before JOIN.

Q25

Multiple Choice

Which SQL code snippet correctly follows the SQL execution order for using subqueries in the SELECT clause?

SQL Code

SELECT e.employee_id, e.first_name,
(SELECT department_name FROM departments d WHERE d.department_id = e.department_id) AS department_name
FROM employees e
WHERE e.salary > 5000
ORDER BY e.first_name;

SELECT e.employee_id, e.first_name, (SELECT department_name FROM departments d WHERE d.department_id = e.department_id) AS department_name FROM employees e WHERE e.salary > 5000 ORDER BY e.first_name; SELECT e.employee_id, e.first_name, (SELECT department_name FROM departments d WHERE d.department_id = e.department_id) AS department_name FROM employees e WHERE e.salary > 5000 ORDER BY e.first_name; SELECT e.employee_id, e.first_name, (SELECT department_name FROM departments d WHERE d.department_id = e.department_id) AS department_name FROM employees e WHERE e.salary > 5000 ORDER BY e.first_name;SELECT e.employee_id, e.first_name, (SELECT department_name FROM departments d WHERE d.salary > 5000 AND d.department_id = e.department_id) AS department_name FROM employees e ORDER BY e.first_name;

The correct execution order is FROM -> WHERE -> (Subquery in SELECT) -> SELECT -> ORDER BY. Options A, B, and C follow this order correctly, while option D incorrectly places WHERE inside the subquery.

Q26

Multiple Choice

Which SQL code snippet demonstrates advanced SQL execution order by using a window function after a join operation?

SQL Code

SELECT e.employee_id, e.first_name, d.department_name,
RANK() OVER (PARTITION BY d.department_id ORDER BY e.salary DESC) AS rank
FROM employees e
JOIN departments d ON e.department_id = d.department_id
ORDER BY e.first_name;

SELECT e.employee_id, e.first_name, d.department_name, RANK() OVER (PARTITION BY d.department_id ORDER BY e.salary DESC) AS rank FROM employees e JOIN departments d ON e.department_id = d.department_id ORDER BY e.first_name; SELECT e.employee_id, e.first_name, d.department_name, RANK() OVER (PARTITION BY d.department_id ORDER BY e.salary DESC) AS rank FROM employees e JOIN departments d ON e.department_id = d.department_id ORDER BY e.first_name; SELECT e.employee_id, e.first_name, d.department_name, RANK() OVER (PARTITION BY d.department_id ORDER BY e.salary DESC) AS rank FROM employees e JOIN departments d ON e.department_id = d.department_id ORDER BY e.first_name;SELECT e.employee_id, e.first_name, RANK() OVER (ORDER BY e.salary DESC) AS rank, d.department_name FROM employees e ORDER BY e.first_name JOIN departments d ON e.department_id = d.department_id;

The correct execution order is FROM -> JOIN -> SELECT -> WINDOW FUNCTION -> ORDER BY. Options A, B, and C follow this order correctly, while option D incorrectly places the window function before the JOIN.

Q27

Multiple Choice

Which SQL code snippet demonstrates advanced SQL execution order by using a CTE (Common Table Expression) before performing a join?

SQL Code

WITH DepartmentSalaries AS (
SELECT department_id, AVG(salary) AS avg_salary
FROM employees
GROUP BY department_id)
SELECT e.employee_id, e.first_name, ds.avg_salary
FROM employees e
JOIN DepartmentSalaries ds ON e.department_id = ds.department_id
ORDER BY e.first_name;

WITH DepartmentSalaries AS ( SELECT department_id, AVG(salary) AS avg_salary FROM employees GROUP BY department_id) SELECT e.employee_id, e.first_name, ds.avg_salary FROM employees e JOIN DepartmentSalaries ds ON e.department_id = ds.department_id ORDER BY e.first_name; WITH DepartmentSalaries AS ( SELECT department_id, AVG(salary) AS avg_salary FROM employees GROUP BY department_id) SELECT e.employee_id, e.first_name, ds.avg_salary FROM employees e JOIN DepartmentSalaries ds ON e.department_id = ds.department_id ORDER BY e.first_name; WITH DepartmentSalaries AS ( SELECT department_id, AVG(salary) AS avg_salary FROM employees GROUP BY department_id) SELECT e.employee_id, e.first_name, ds.avg_salary FROM employees e JOIN DepartmentSalaries ds ON e.department_id = ds.department_id ORDER BY e.first_name;SELECT e.employee_id, e.first_name, ds.avg_salary WITH DepartmentSalaries AS ( SELECT department_id, AVG(salary) AS avg_salary FROM employees GROUP BY department_id) FROM employees e JOIN DepartmentSalaries ds ON e.department_id = ds.department_id ORDER BY e.first_name;

The correct execution order is CTE -> FROM -> JOIN -> SELECT -> ORDER BY. Options A, B, and C follow this order correctly, while option D incorrectly places the CTE after the SELECT statement.

Q28

Multiple Choice

Which SQL code snippet demonstrates certification-level SQL execution order by applying multiple WHERE conditions before a join?

SQL Code

SELECT e.employee_id, e.first_name, d.department_name
FROM employees e
JOIN departments d ON e.department_id = d.department_id
WHERE e.salary > 5000 AND e.hire_date > '01-JAN-2020'
ORDER BY e.first_name;

SELECT e.employee_id, e.first_name, d.department_name FROM employees e JOIN departments d ON e.department_id = d.department_id WHERE e.salary > 5000 AND e.hire_date > '01-JAN-2020' ORDER BY e.first_name; SELECT e.employee_id, e.first_name, d.department_name FROM employees e JOIN departments d ON e.department_id = d.department_id WHERE e.salary > 5000 AND e.hire_date > '01-JAN-2020' ORDER BY e.first_name; SELECT e.employee_id, e.first_name, d.department_name FROM employees e JOIN departments d ON e.department_id = d.department_id WHERE e.salary > 5000 AND e.hire_date > '01-JAN-2020' ORDER BY e.first_name;SELECT e.employee_id, e.first_name, d.department_name FROM employees e WHERE e.salary > 5000 AND e.hire_date > '01-JAN-2020' JOIN departments d ON e.department_id = d.department_id ORDER BY e.first_name;

The correct execution order is FROM -> WHERE -> JOIN -> SELECT -> ORDER BY. Options A, B, and C follow this order correctly, while option D incorrectly places WHERE after the JOIN.

Q29

Multiple Choice

Which SQL code snippet demonstrates certification-level SQL execution order by using a subquery in the WHERE clause?

SQL Code

SELECT employee_id, first_name
FROM employees
WHERE department_id IN (
SELECT department_id FROM departments WHERE location_id = 1700)
ORDER BY first_name;

SELECT employee_id, first_name FROM employees WHERE department_id IN ( SELECT department_id FROM departments WHERE location_id = 1700) ORDER BY first_name; SELECT employee_id, first_name FROM employees WHERE department_id IN ( SELECT department_id FROM departments WHERE location_id = 1700) ORDER BY first_name; SELECT employee_id, first_name FROM employees WHERE department_id IN ( SELECT department_id FROM departments WHERE location_id = 1700) ORDER BY first_name;SELECT employee_id, first_name WHERE department_id IN ( SELECT department_id FROM departments WHERE location_id = 1700) FROM employees ORDER BY first_name;

The correct execution order is FROM -> (Subquery in WHERE) -> WHERE -> SELECT -> ORDER BY. Options A, B, and C follow this order correctly, while option D incorrectly places SELECT before WHERE.

Q30

Multiple Choice

Which SQL code snippet demonstrates certification-level SQL execution order by using the GROUP BY clause with a HAVING filter?

SQL Code

SELECT department_id, AVG(salary) AS avg_salary
FROM employees
GROUP BY department_id
HAVING AVG(salary) > 5000
ORDER BY department_id;

SELECT department_id, AVG(salary) AS avg_salary FROM employees GROUP BY department_id HAVING AVG(salary) > 5000 ORDER BY department_id; SELECT department_id, AVG(salary) AS avg_salary FROM employees GROUP BY department_id HAVING AVG(salary) > 5000 ORDER BY department_id; SELECT department_id, AVG(salary) AS avg_salary FROM employees GROUP BY department_id HAVING AVG(salary) > 5000 ORDER BY department_id;SELECT department_id, AVG(salary) AS avg_salary FROM employees HAVING AVG(salary) > 5000 GROUP BY department_id ORDER BY department_id;

The correct execution order is FROM -> GROUP BY -> HAVING -> SELECT -> ORDER BY. Options A, B, and C follow this order correctly, while option D incorrectly places HAVING before GROUP BY.

Oracle Database Quiz Questions