Why CRUD operations are fundamental in PostgreSQL - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

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

PostgreSQL

SELECT [1] FROM employees;

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

A*

BALL

Ccolumns

Deverything

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'ALL' instead of '*'

Writing 'columns' which is not valid SQL syntax

The asterisk (*) means select all columns from the table.

2fill in blank

medium

Complete the code to insert a new row into the 'employees' table with name 'John' and age 30.

PostgreSQL

INSERT INTO employees (name, age) VALUES ([1]);

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A(John, 30)

BJohn, 30

C'John', '30'

D'John', 30

Attempts:

3 left

💡 Hint

Common Mistakes

Not using quotes around string values

Including extra parentheses inside VALUES

Values must be in parentheses and strings in single quotes. Numbers do not need quotes.

3fill in blank

hard

Fix the error in the code to update the age of employee 'John' to 31.

PostgreSQL

UPDATE employees SET age = [1] WHERE name = 'John';

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

A31

B"31"

C'31'

Dage + 1

Attempts:

3 left

💡 Hint

Common Mistakes

Putting numbers in quotes

Using double quotes instead of single quotes for strings

Numbers should not be in quotes in SQL UPDATE statements.

4fill in blank

hard

Fill both blanks to delete rows where age is less than 25.

PostgreSQL

DELETE FROM employees WHERE age [1] [2];

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A<

B>

C25

D30

Attempts:

3 left

💡 Hint

Common Mistakes

Using greater than symbol instead of less than

Using wrong number for comparison

The condition deletes rows where age is less than 25.

5fill in blank

hard

Fill all three blanks to select the name and age of employees older than 40.

PostgreSQL

SELECT [1], [2] FROM employees WHERE age [3] 40;

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

Aname

Bage

C>

Dname, age

Attempts:

3 left

💡 Hint

Common Mistakes

Selecting only one column

Using less than symbol instead of greater than

Select the columns 'name' and 'age' and filter where age is greater than 40.