Test Your PostgreSQL DELETE Command Knowledge with This Quiz

Progress

True / False

In PostgreSQL, the DELETE statement is used to remove rows from a table.

True False

The DELETE statement is used to remove existing records from a table in PostgreSQL.

True / False

You must specify a WHERE clause in a DELETE statement to remove rows from a table.

True False

While it is common to use a WHERE clause to specify which rows to delete, it is not required. If omitted, all rows in the table will be deleted.

True / False

The DELETE statement can only be used on a single table in PostgreSQL.

True False

In PostgreSQL, the DELETE statement is designed to delete rows from a single table.

True / False

In PostgreSQL, you can use a RETURNING clause with the DELETE statement to return deleted rows.

True False

The RETURNING clause can be used with DELETE to return the deleted rows or specific columns of the deleted rows.

True / False

The DELETE statement in PostgreSQL can be rolled back if used within a transaction block.

True False

If a DELETE statement is used within a transaction block, it can be rolled back using the ROLLBACK command.

True / False

You can use subqueries in the WHERE clause of a DELETE statement in PostgreSQL.

True False

Subqueries can be used in the WHERE clause of a DELETE statement to specify the rows to be deleted based on the results of the subquery.

True / False

In PostgreSQL, the DELETE statement can reference multiple tables using the USING clause.

True False

The USING clause can be used in a DELETE statement to reference multiple tables for the purpose of specifying conditions in the WHERE clause.

True / False

In PostgreSQL, you cannot use JOINs in a DELETE statement.

True False

PostgreSQL supports the use of JOINs in DELETE statements, allowing you to delete rows from one table based on conditions in another table.

True / False

The DELETE statement in PostgreSQL can be used with CTE (Common Table Expressions).

True False

PostgreSQL allows the use of CTEs in DELETE statements to simplify complex queries.

Q10

True / False

In PostgreSQL, the DELETE statement with a RETURNING clause can be used to capture the old and new values of the deleted rows for auditing purposes.

True False

The RETURNING clause in a DELETE statement can only return the old values (the values before deletion). It does not capture new values because the rows are being deleted.

Q11

Single Choice

What does the DELETE statement do in PostgreSQL?

Deletes a table Deletes specific rows from a table Deletes a databaseDeletes columns from a table

In PostgreSQL, the DELETE statement is used to remove rows from a table based on a specified condition.

Q12

Single Choice

Which of the following is the correct syntax to delete all rows from a table named employees in PostgreSQL?

REMOVE FROM employees; DROP TABLE employees DELETE FROM employees;TRUNCATE employees;

The DELETE FROM statement is used to delete all rows from the employees table in PostgreSQL.

Q13

Single Choice

What keyword is used in PostgreSQL to delete rows that meet a specific condition?

WHERE FROM IFWHEN

The WHERE clause is used in the DELETE statement to specify the condition that rows must meet to be deleted.

Q14

Single Choice

Which of the following DELETE statements will remove employees with a salary greater than 50000 in PostgreSQL?

DELETE FROM employees WHERE salary >= 50000; DELETE FROM employees WHERE salary > 50000; DELETE FROM employees WHERE salary <= 50000DELETE FROM employees WHERE salary = 50000;

The correct DELETE statement includes the WHERE clause that specifies the condition to remove rows where the salary is greater than 50000.

Q15

Single Choice

In PostgreSQL, what happens if you execute the following command: DELETE FROM orders WHERE order_id IN (SELECT order_id FROM shipped_orders);?

It deletes all rows from the orders table It deletes rows from the orders table that are also in the shipped_orders table. It deletes rows from the orders table that are also in the shipped_orders table.It deletes rows from the shipped_orders table.

This command deletes rows from the orders table where order_id matches the order_id in the shipped_orders table.

Q16

Single Choice

Which of the following is true about using DELETE in PostgreSQL with a RETURNING clause?

DELETE can return the number of rows deleted. DELETE cannot use the RETURNING clause. DELETE with RETURNING returns the columns specified.DELETE will always return all columns

The RETURNING clause in PostgreSQL can be used with DELETE to return specific columns from the rows that were deleted

Q17

Single Choice

What does the following PostgreSQL command do?

SQL Code

DELETE FROM products p
USING categories c
WHERE p.category_id = c.id AND c.name = 'Obsolete';

Deletes all rows in the categories table. Deletes all rows in the products table where category_id matches the id of 'Obsolete' category. Deletes all rows in both products and categories tablesDeletes all rows where category_id does not match the id of 'Obsolete' category.

The DELETE statement with the USING clause is used to delete rows in the products table where the category_id matches the id of the 'Obsolete' category in the categories table.

Q18

Single Choice

How can you ensure that a DELETE operation in PostgreSQL does not delete any rows if the subquery returns no results?

Use DELETE FROM table WHERE EXISTS (subquery) Use DELETE FROM table WHERE NOT EXISTS (subquery); Use DELETE FROM table WHERE condition;Use DELETE FROM table WHERE subquery;

: The EXISTS keyword ensures that the DELETE operation only occurs if the subquery returns results.

Q19

Single Choice

Given the following tables orders and customers, how would you delete all orders for customers in a specific city, 'New York'?

SQL Code

DELETE FROM orders
WHERE customer_id IN (
 SELECT id
 FROM customers
 WHERE city = 'New York'
);

Deletes all orders from the orders table. Deletes orders from customers in 'New York'. Deletes customers from 'New York'Deletes nothing

The subquery finds all customer IDs from 'New York', and the DELETE statement removes orders associated with those customers.

Q20

Single Choice

What will the following PostgreSQL command do?

SQL Code

DELETE FROM inventory i
WHERE EXISTS (
 SELECT 1
 FROM warehouse w
 WHERE w.item_id = i.item_id
 AND w.stock < 0
);

Deletes all rows from warehouse where stock is less than 0. Deletes all rows from inventory where there is a corresponding item_id in warehouse with stock less than 0. Deletes all rows from inventory.Deletes nothing

The EXISTS clause checks for item_id in the warehouse with stock less than 0, and if found, deletes the corresponding rows from the inventory table.

Q21

Multiple Choice

Which SQL command deletes a single row from a PostgreSQL table based on a specific condition?

SQL Code

DELETE FROM employees
WHERE employee_id = 1;

DELETE FROM employees WHERE employee_id = 1; DELETE FROM employees WHERE employee_id = 'John'; DELETE FROM employees;DELETE FROM employees WHERE first_name = 'John';

This command deletes the row from the 'employees' table where the 'employee_id' equals 1.

Q22

Multiple Choice

Which SQL command deletes multiple rows from a PostgreSQL table that meet a specific condition?

SQL Code

DELETE FROM orders
WHERE order_date < '2023-01-01';

DELETE FROM orders WHERE order_date < '2023-01-01'; DELETE FROM orders WHERE order_date = '2023-01-01'; DELETE FROM orders;DELETE FROM orders WHERE order_date > '2023-01-01';

This command deletes all rows from the 'orders' table where the 'order_date' is earlier than '2023-01-01'.

Q23

Multiple Choice

Which SQL command deletes rows in a PostgreSQL table based on a condition with a subquery?

SQL Code

DELETE FROM employees
WHERE department_id = (
 SELECT department_id FROM departments WHERE department_name = 'HR'
);

DELETE FROM employees WHERE department_id = ( SELECT department_id FROM departments WHERE department_name = 'HR' ); DELETE FROM employees WHERE department_name = 'HR'; DELETE FROM employees;DELETE FROM employees WHERE department_id = 1;

This command deletes rows from the 'employees' table where the 'department_id' matches the 'department_id' of the 'HR' department as returned by a subquery.

Q24

Multiple Choice

Which SQL command deletes all rows from a PostgreSQL table?

SQL Code

DELETE FROM customers;

DELETE FROM customers; DELETE * FROM customers; DELETE FROM customers WHERE customer_id > 0;TRUNCATE TABLE customers;

This command deletes all rows from the 'customers' table, leaving the table empty but intact.

Q25

Multiple Choice

Which SQL command deletes rows in a PostgreSQL table and returns the deleted rows using the RETURNING clause?

SQL Code

DELETE FROM employees
WHERE department_id = 2
RETURNING employee_id, first_name, last_name;

DELETE FROM employees WHERE department_id = 2 RETURNING employee_id, first_name, last_name; DELETE FROM employees WHERE department_id = 2; DELETE FROM employees RETURNING employee_id, first_name, last_name;DELETE FROM employees WHERE department_id = 2 RETURNING *;

This command deletes rows from the 'employees' table where 'department_id' equals 2 and returns the 'employee_id', 'first_name', and 'last_name' of the deleted rows.

Q26

Multiple Choice

Which SQL command deletes rows from a table in PostgreSQL using a JOIN clause?

SQL Code

DELETE FROM orders o
USING customers c
WHERE o.customer_id = c.customer_id
AND c.customer_name = 'John Doe';

DELETE FROM orders o USING customers c WHERE o.customer_id = c.customer_id AND c.customer_name = 'John Doe'; DELETE FROM orders o WHERE customer_id = (SELECT customer_id FROM customers WHERE customer_name = 'John Doe'); DELETE FROM orders o WHERE customer_name = 'John Doe';DELETE FROM orders o USING customers c WHERE o.customer_id = c.customer_id;

This command deletes rows from the 'orders' table where the 'customer_id' matches 'John Doe' in the 'customers' table using a JOIN operation.

Q27

Multiple Choice

Which SQL command deletes rows from a PostgreSQL table where a certain value is NULL?

SQL Code

DELETE FROM orders
WHERE shipping_date IS NULL;

DELETE FROM orders WHERE shipping_date IS NULL; DELETE FROM orders WHERE shipping_date = NULL; DELETE FROM orders WHERE shipping_date IS NOT NULL;DELETE FROM orders;

This command deletes rows from the 'orders' table where the 'shipping_date' column is NULL.

Q28

Multiple Choice

Which SQL command deletes rows from a PostgreSQL table based on a condition using EXISTS?

SQL Code

DELETE FROM employees e
WHERE EXISTS (
 SELECT 1 FROM departments d WHERE d.department_id = e.department_id AND d.department_name = 'HR'
);

DELETE FROM employees e WHERE EXISTS ( SELECT 1 FROM departments d WHERE d.department_id = e.department_id AND d.department_name = 'HR' ); DELETE FROM employees e WHERE EXISTS ( SELECT 1 FROM departments WHERE department_name = 'HR' ); DELETE FROM employees e WHERE EXISTS ( SELECT 1 FROM departments d WHERE d.department_id = e.department_id );DELETE FROM employees e WHERE department_name = 'HR';

This command deletes rows from the 'employees' table where the 'department_id' exists in the 'departments' table with the name 'HR'.

Q29

Multiple Choice

Which SQL command deletes rows from a PostgreSQL table and logs the deleted data using the RETURNING clause?

SQL Code

DELETE FROM inventory
WHERE product_id = 404
RETURNING *;

DELETE FROM inventory WHERE product_id = 404 RETURNING *; DELETE FROM inventory WHERE product_id = 404; DELETE FROM inventory RETURNING *;DELETE FROM inventory WHERE product_id = 404 RETURNING product_id;

This command deletes rows from the 'inventory' table where 'product_id' equals 404 and returns all columns of the deleted rows.

Q30

Multiple Choice

Which SQL command deletes rows from a table in PostgreSQL using a CTE (Common Table Expression)?

SQL Code

WITH old_orders AS (
 SELECT order_id FROM orders WHERE order_date < '2022-01-01'
)
DELETE FROM orders
WHERE order_id IN (SELECT order_id FROM old_orders);

WITH old_orders AS ( SELECT order_id FROM orders WHERE order_date < '2022-01-01' ) DELETE FROM orders WHERE order_id IN (SELECT order_id FROM old_orders); WITH old_orders AS ( SELECT order_id FROM orders WHERE order_date < '2022-01-01' ) DELETE FROM old_orders; DELETE FROM orders WHERE order_id IN (SELECT order_id FROM orders WHERE order_date < '2022-01-01');WITH old_orders AS ( SELECT order_id FROM orders WHERE order_date < '2022-01-01' ) DELETE FROM orders;

This command uses a CTE named 'old_orders' to identify rows in the 'orders' table with an 'order_date' earlier than '2022-01-01' and deletes them.

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