Test Your PostgreSQL UPDATE Command Knowledge with This Quiz

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True / False

The UPDATE statement in PostgreSQL can be used to change existing records in a table.

True False

The UPDATE statement is used to modify existing records in a table in PostgreSQL.

True / False

In PostgreSQL, the UPDATE statement must include the WHERE clause.

True False

The WHERE clause is optional in an UPDATE statement. However, omitting it will result in updating all rows in the table.

True / False

The SET keyword is used in PostgreSQL UPDATE statements to specify the columns and new values.

True False

The SET keyword is used to define the columns and their new values in an UPDATE statement.

True / False

In PostgreSQL, you can use subqueries in the SET clause of an UPDATE statement.

True False

Subqueries can be used in the SET clause to dynamically determine the new values for the columns being updated.

True / False

PostgreSQL allows you to update multiple columns in a single UPDATE statement.

True False

You can update multiple columns by separating each column and value pair with a comma in the SET clause.

True / False

You cannot use the RETURNING clause in a PostgreSQL UPDATE statement to return the updated rows.

True False

The RETURNING clause can be used in an UPDATE statement to return the updated rows.

True / False

PostgreSQL supports the use of common table expressions (CTEs) with UPDATE statements.

True False

Common Table Expressions (CTEs) can be used in conjunction with UPDATE statements to make complex queries more readable and manageable.

True / False

In PostgreSQL, it is possible to perform an UPDATE on a table and use the FROM clause to join with other tables.

True False

The FROM clause can be used in an UPDATE statement to join with other tables, allowing for more complex updates based on related data.

True / False

PostgreSQL automatically creates an index on columns that are frequently updated.

True False

PostgreSQL does not automatically create indexes on frequently updated columns. Indexes must be created manually as needed.

Q10

True / False

PostgreSQL’s UPDATE statement does not support the USING clause to join tables during the update operation.

True False

PostgreSQL supports the USING clause in UPDATE statements to join tables during the update operation, providing a way to update based on related data.

Q11

Single Choice

What is the correct syntax to update a single column value in PostgreSQL?

SQL Code

UPDATE employees
SET salary = 50000
WHERE id = 1;

UPDATE employees salary SET = 50000 WHERE id = 1; UPDATE employees SET salary = 50000 WHERE id = 1 SET salary = 50000 UPDATE employees WHERE id = 1;MODIFY employees SET salary = 50000 WHERE id = 1;

The correct syntax to update a column in PostgreSQL is UPDATE table_name SET column_name = value WHERE condition;.

Q12

Single Choice

What will happen if you omit the WHERE clause in a PostgreSQL UPDATE statement?

Only the first row will be updated. All rows in the table will be updated. No rows will be updated.An error will occur

Omitting the WHERE clause in an UPDATE statement causes PostgreSQL to update all rows in the table.

Q13

Single Choice

Which keyword is used in a PostgreSQL UPDATE statement to change the value of a column?

MODIFY CHANGE SETALTER

The SET keyword is used in the UPDATE statement to assign a new value to a column in PostgreSQL.

Q14

Single Choice

How do you update multiple columns in a PostgreSQL table?

SQL Code

UPDATE employees
SET salary = 60000, position = 'Manager'
WHERE id = 2;

UPDATE employees SET salary = 60000 AND position = 'Manager' WHERE id = 2; UPDATE employees MODIFY salary = 60000, position = 'Manager' WHERE id = 2; UPDATE employees SET salary = 60000, position = 'Manager' WHERE id = 2;UPDATE employees CHANGE salary = 60000, position = 'Manager' WHERE id = 2;

To update multiple columns, use the SET keyword followed by column-value pairs separated by commas.

Q15

Single Choice

How can you update a column in PostgreSQL using data from another table?

SQL Code

UPDATE employees
SET salary = departments.avg_salary
FROM departments
WHERE employees.department_id = departments.id
AND departments.name = 'Sales';

UPDATE employees SET salary = departments.avg_salary WHERE employees.department_id = departments.id AND departments.name = 'Sales'; UPDATE employees SET salary = (SELECT avg_salary FROM departments WHERE employees.department_id = departments.id AND departments.name = 'Sales'); UPDATE employees SET salary = departments.avg_salary FROM departments WHERE employees.department_id = departments.id AND departments.name = 'Sales';UPDATE employees SET salary = departments.avg_salary WHERE employees.department_id = departments.id;

UPDATE employees SET salary = departments.avg_salary WHERE employees.department_id = departments.id;

Q16

Single Choice

What happens when you update a row that does not satisfy the WHERE condition in PostgreSQL?

The row is updated with NULL values The row is updated with the default values. No rows are updated.An error is thrown

If no rows match the WHERE condition, the UPDATE statement does not update any rows.

Q17

Single Choice

How do you use a subquery in the SET clause of a PostgreSQL UPDATE statement?

SQL Code

UPDATE employees
SET salary = (SELECT MAX(salary) FROM employees WHERE department_id = 2)
WHERE department_id = 2;

UPDATE employees SET salary = (SELECT MAX(salary) FROM employees WHERE department_id = 2) WHERE department_id = 2; UPDATE employees SET salary = (MAX(salary) FROM employees WHERE department_id = 2) WHERE department_id = 2; UPDATE employees SET salary = SELECT MAX(salary) WHERE department_id = 2 FROM employees WHERE department_id = 2;UPDATE employees SET salary = (SELECT MAX(salary) WHERE department_id = 2) WHERE department_id = 2;

You can use a subquery in the SET clause by enclosing it in parentheses, which returns a single value to be assigned.

Q18

Single Choice

How can you safely update rows in PostgreSQL with a condition that includes NULL values?

SQL Code

UPDATE employees
SET salary = 45000
WHERE department_id IS NULL;

UPDATE employees SET salary = 45000 WHERE department_id IS NULL; UPDATE employees SET salary = 45000 WHERE department_id = NULL; UPDATE employees SET salary = 45000 WHERE department_id NULL;UPDATE employees SET salary = 45000 WHERE department_id EQUALS NULL;

To check for NULL values in PostgreSQL, use the IS NULL condition in the WHERE clause.

Q19

Single Choice

How do you conditionally update rows in PostgreSQL based on a complex condition?

SQL Code

UPDATE employees
SET bonus = CASE
 WHEN performance = 'Excellent' THEN 1000
 WHEN performance = 'Good' THEN 500
 ELSE 0
END
WHERE department_id = 3;

UPDATE employees SET bonus = CASE performance WHEN 'Excellent' THEN 1000 WHEN 'Good' THEN 500 ELSE 0 END WHERE department_id = 3; UPDATE employees SET bonus = CASE WHEN performance = 'Excellent' THEN 1000 WHEN performance = 'Good' THEN 500 ELSE 0 END WHERE department_id = 3; UPDATE employees SET bonus = CASE WHEN 'Excellent' THEN 1000 WHEN 'Good' THEN 500 ELSE 0 END WHERE department_id = 3;UPDATE employees SET bonus = CASE IF performance = 'Excellent' THEN 1000 IF performance = 'Good' THEN 500 ELSE 0 END WHERE department_id = 3;

The CASE statement is used in the SET clause to conditionally update rows based on specific conditions.

Q20

Single Choice

How can you update rows in PostgreSQL and return the updated rows as a result?

SQL Code

UPDATE employees
SET salary = salary * 1.10
WHERE department_id = 4
RETURNING *;

UPDATE employees SET salary = salary * 1.10 WHERE department_id = 4; UPDATE employees SET salary = salary * 1.10 WHERE department_id = 4 RETURNING salary; UPDATE employees SET salary = salary * 1.10 WHERE department_id = 4 RETURNING *;UPDATE employees SET salary = salary * 1.10 WHERE department_id = 4 RETURNING id, salary;

The RETURNING * clause is used in PostgreSQL to return the updated rows as a result after executing the UPDATE statement.

Q21

Multiple Choice

Which SQL command updates a single column in a PostgreSQL table?

SQL Code

UPDATE employees
SET salary = 60000
WHERE employee_id = 1;

UPDATE employees SET salary = 60000 WHERE employee_id = 1; UPDATE employees SET salary = 60000; UPDATE employees SET salary = 60000 WHERE employee_id = 'John';UPDATE employees SET employee_id = 1 WHERE salary = 60000;

This command updates the 'salary' column of the 'employees' table for the row where 'employee_id' equals 1.

Q22

Multiple Choice

Which SQL command updates multiple columns in a PostgreSQL table?

SQL Code

UPDATE products
SET price = 19.99, stock = stock - 1
WHERE product_id = 101;

UPDATE products SET price = 19.99, stock = stock - 1 WHERE product_id = 101; UPDATE products SET price = 19.99, stock = stock - 1; UPDATE products SET price = 19.99 WHERE product_id = 101;UPDATE products SET stock = stock - 1 WHERE product_id = 101;

This command updates the 'price' and 'stock' columns in the 'products' table for the row where 'product_id' equals 101.

Q23

Multiple Choice

Which SQL command uses a subquery to update a PostgreSQL table?

SQL Code

UPDATE employees
SET department_id = (
 SELECT department_id FROM departments WHERE department_name = 'HR'
)
WHERE employee_id = 1;

UPDATE employees SET department_id = ( SELECT department_id FROM departments WHERE department_name = 'HR' ) WHERE employee_id = 1; UPDATE employees SET department_id = 1 WHERE employee_id = 1; UPDATE employees SET department_id = ( SELECT department_id FROM departments ) WHERE employee_id = 1;UPDATE employees SET department_id = 'HR' WHERE employee_id = 1;

This command updates the 'department_id' of an employee in the 'employees' table by using a subquery to select the 'department_id' from the 'departments' table where the 'department_name' is 'HR'.

Q24

Multiple Choice

Which SQL command updates a table in PostgreSQL using data from another table?

SQL Code

UPDATE sales
SET total_amount = orders.total_amount
FROM orders
WHERE sales.order_id = orders.order_id;

UPDATE sales SET total_amount = orders.total_amount FROM orders WHERE sales.order_id = orders.order_id; UPDATE sales SET total_amount = orders.total_amount; UPDATE sales SET total_amount = ( SELECT total_amount FROM orders WHERE sales.order_id = orders.order_id );UPDATE sales SET total_amount = ( SELECT total_amount FROM orders );

This command updates the 'total_amount' column in the 'sales' table by using data from the 'orders' table, where 'order_id' matches.

Q25

Multiple Choice

Which SQL command updates a column conditionally using a CASE statement in PostgreSQL?

SQL Code

UPDATE employees
SET bonus = CASE
 WHEN department_id = 1 THEN 500
 WHEN department_id = 2 THEN 300
 ELSE 100
END;

UPDATE employees SET bonus = CASE WHEN department_id = 1 THEN 500 WHEN department_id = 2 THEN 300 ELSE 100 END; UPDATE employees SET bonus = CASE WHEN department_id = 1 THEN 500 ELSE 100 END; UPDATE employees SET bonus = 500 WHERE department_id = 1;UPDATE employees SET bonus = 100 WHERE department_id != 1 AND department_id != 2;

This command updates the 'bonus' column in the 'employees' table conditionally using a CASE statement, providing different values based on the 'department_id'.

Q26

Multiple Choice

Which SQL command updates a column by incrementing its value in PostgreSQL?

SQL Code

UPDATE inventory
SET stock = stock + 10
WHERE product_id = 202;

UPDATE inventory SET stock = stock + 10 WHERE product_id = 202; UPDATE inventory SET stock = stock + 10; UPDATE inventory SET stock = 10 WHERE product_id = 202;UPDATE inventory SET stock = stock + 10 WHERE product_id = 101;

This command updates the 'stock' column in the 'inventory' table by incrementing its value by 10 for the row where 'product_id' equals 202.

Q27

Multiple Choice

Which SQL command updates a table in PostgreSQL by setting a column to a NULL value?

SQL Code

UPDATE orders
SET shipping_date = NULL
WHERE order_id = 305;

UPDATE orders SET shipping_date = NULL WHERE order_id = 305; UPDATE orders SET shipping_date = 'NULL' WHERE order_id = 305; UPDATE orders SET shipping_date = NULL;UPDATE orders SET shipping_date = 'NULL';

This command updates the 'shipping_date' column in the 'orders' table by setting it to NULL for the row where 'order_id' equals 305.

Q28

Multiple Choice

Which SQL command updates a table in PostgreSQL using a JOIN clause?

SQL Code

UPDATE employees e
SET e.salary = s.new_salary
FROM salary_updates s
WHERE e.employee_id = s.employee_id;

UPDATE employees e SET e.salary = s.new_salary FROM salary_updates s WHERE e.employee_id = s.employee_id; UPDATE employees SET salary = new_salary WHERE employee_id = (SELECT employee_id FROM salary_updates); UPDATE employees e SET salary = (SELECT new_salary FROM salary_updates s WHERE e.employee_id = s.employee_id);UPDATE employees SET salary = (SELECT new_salary FROM salary_updates WHERE employee_id = employees.employee_id);

This command updates the 'salary' column in the 'employees' table by using a JOIN with the 'salary_updates' table, matching rows on 'employee_id'.

Q29

Multiple Choice

Which SQL command updates a table and logs the old values using the RETURNING clause in PostgreSQL?

SQL Code

UPDATE employees
SET salary = salary * 1.05
WHERE department_id = 3
RETURNING employee_id, old_salary = salary / 1.05;

UPDATE employees SET salary = salary * 1.05 WHERE department_id = 3 RETURNING employee_id, old_salary = salary / 1.05; UPDATE employees SET salary = salary * 1.05 WHERE department_id = 3; UPDATE employees SET salary = salary * 1.05 RETURNING employee_id, old_salary = salary / 1.05;UPDATE employees SET salary = salary * 1.05 WHERE department_id = 3 RETURNING employee_id, salary;

This command updates the 'salary' column in the 'employees' table by increasing it by 5% for the department with 'department_id' 3 and returns the 'employee_id' and the old salary values.

Q30

Multiple Choice

Which SQL command uses an UPDATE statement to set a column value conditionally and ensure no conflict occurs in PostgreSQL?

SQL Code

UPDATE customers
SET email = 'new_email@example.com'
WHERE NOT EXISTS (
 SELECT 1 FROM customers WHERE email = 'new_email@example.com'
) AND customer_id = 42;

UPDATE customers SET email = 'new_email@example.com' WHERE NOT EXISTS ( SELECT 1 FROM customers WHERE email = 'new_email@example.com' ) AND customer_id = 42; UPDATE customers SET email = 'new_email@example.com' WHERE email != 'new_email@example.com' AND customer_id = 42; UPDATE customers SET email = 'new_email@example.com' WHERE customer_id = 42;UPDATE customers SET email = 'new_email@example.com' WHERE NOT EXISTS ( SELECT 1 FROM customers WHERE customer_id = 42 );

This command updates the 'email' column in the 'customers' table for the customer with 'customer_id' 42, but only if the new email does not already exist in the table.

PostgreSQL Database Quiz Questions