Why PostgreSQL over other databases - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to select all columns from a table named employees.

PostgreSQL

SELECT [1] FROM employees;

Drag options to blanks, or click blank then click option'

A*

Ball

Ceverything

Dcolumns

Attempts:

3 left

💡 Hint

Common Mistakes

Using words like 'all' or 'columns' instead of the symbol *.

Leaving the blank empty.

In SQL, * means select all columns from the table.

2fill in blank

medium

Complete the code to filter employees with salary greater than 50000.

PostgreSQL

SELECT * FROM employees WHERE salary [1] 50000;

Drag options to blanks, or click blank then click option'

A<=

B<

C=

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Using < or <= which select smaller or equal values.

Using = which selects only equal values.

The symbol > means 'greater than' in SQL conditions.

3fill in blank

hard

Fix the error in the code to count employees in each department.

PostgreSQL

SELECT department, COUNT([1]) FROM employees GROUP BY department;

Drag options to blanks, or click blank then click option'

Asalary

B*

Cdepartment

Demployee_id

Attempts:

3 left

💡 Hint

Common Mistakes

Counting a specific column which may have NULLs and cause wrong counts.

Using a column that is not unique or relevant.

Using COUNT(*) counts all rows in each group, which is standard for counting employees.

4fill in blank

hard

Fill both blanks to create a table named products with id as primary key.

PostgreSQL

CREATE TABLE products (id [1] PRIMARY KEY, name [2] NOT NULL);

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ASERIAL

BVARCHAR(100)

CINTEGER

DTEXT

Attempts:

3 left

💡 Hint

Common Mistakes

Using TEXT for id which does not auto-increment.

Using INTEGER for name which is not text.

SERIAL creates an auto-incrementing integer for id. VARCHAR(100) defines a text column with max 100 characters for name.

5fill in blank

hard

Fill all three blanks to update the salary of employee with id 10 to 60000.

PostgreSQL

UPDATE employees SET salary = [1] WHERE id [2] [3];

Drag options to blanks, or click blank then click option'

A50000

B60000

C10

D=

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong salary value.

Using wrong comparison operator.

Swapping id and salary values.

We set salary to 60000, and use = to match employee with id 10.