Why PostgreSQL has rich data types - 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 words like 'all' or 'columns' instead of the symbol *.

Forgetting to specify what to select.

The asterisk (*) symbol selects all columns from the table.

2fill in blank

medium

Complete the code to create a table named 'products' with a column 'price' that stores decimal numbers.

PostgreSQL

CREATE TABLE products (price [1]);

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

ABOOLEAN

BVARCHAR

CDECIMAL

DTEXT

Attempts:

3 left

💡 Hint

Common Mistakes

Using VARCHAR or TEXT which store text, not numbers.

Using BOOLEAN which stores true/false values.

DECIMAL is used to store numbers with decimal points, perfect for prices.

3fill in blank

hard

Fix the error in the code to create a table with a column 'created_at' that stores date and time.

PostgreSQL

CREATE TABLE orders (created_at [1]);

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

ATIME

BDATE

CDATETIME

DTIMESTAMP

Attempts:

3 left

💡 Hint

Common Mistakes

Using DATE which stores only the date without time.

Using TIME which stores only the time without date.

Using DATETIME which is not a PostgreSQL data type.

TIMESTAMP stores both date and time, which is needed for 'created_at'.

4fill in blank

hard

Fill both blanks to create a table 'locations' with a column 'coordinates' that stores geometric points.

PostgreSQL

CREATE TABLE locations (coordinates [1]); -- Use [2] for geometric data type

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

APOINT

BVARCHAR

CINTEGER

DBOOLEAN

Attempts:

3 left

💡 Hint

Common Mistakes

Using VARCHAR or INTEGER which are not geometric types.

Using BOOLEAN which stores true/false values.

POINT is the PostgreSQL data type for geometric points, used for coordinates.

5fill in blank

hard

Fill all three blanks to create a table 'users' with a JSON column 'profile', a UUID column 'user_id', and a boolean column 'active'.

PostgreSQL

CREATE TABLE users (user_id [1], profile [2], active [3]);

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

AJSON

BUUID

CBOOLEAN

DTEXT

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up data types like using TEXT instead of JSON.

Using VARCHAR for UUID or BOOLEAN columns.

UUID is used for unique identifiers, JSON stores structured data, and BOOLEAN stores true/false values.

Practice

1. Why does PostgreSQL provide a wide variety of data types?

easy

A. To force users to use only text data

B. To make the database slower and more complex

C. To limit the types of data users can store

D. To store different kinds of data accurately and efficiently

Solution

1. Step 1: Understand PostgreSQL data types purpose

   PostgreSQL offers many data types to handle various real-world data accurately.

2. Step 2: Analyze the effect of rich data types

   Rich data types help keep data accurate and make queries efficient by matching data to the right type.

3. Final Answer:

   To store different kinds of data accurately and efficiently -> Option D

4. Quick Check:

   Rich data types = Accurate & efficient storage [OK]

Hint: Rich data types match data needs for accuracy [OK]

Common Mistakes:

• Thinking data types slow down the database
• Believing all data should be stored as text
• Assuming fewer data types improve performance

2. Which of the following is the correct way to declare a column with a JSON data type in PostgreSQL?

easy

A. CREATE TABLE data (info jsontext);

B. CREATE TABLE data (info textjson);

C. CREATE TABLE data (info json);

D. CREATE TABLE data (info json_data);

Solution

1. Step 1: Recall PostgreSQL JSON data type syntax

   The correct data type for JSON in PostgreSQL is simply json.

2. Step 2: Check each option's syntax

   Only CREATE TABLE data (info json); uses the exact and valid json type; others are invalid or do not exist.

3. Final Answer:

   CREATE TABLE data (info json); -> Option C

4. Quick Check:

   JSON type syntax = json [OK]

Hint: Use exact PostgreSQL data type names [OK]

Common Mistakes:

• Adding extra words to data type names
• Using non-existent data types
• Confusing JSON with text types

3. Given the table CREATE TABLE measurements (id SERIAL, data jsonb); and the insert INSERT INTO measurements (data) VALUES ('{"temp": 22, "unit": "C"}');, what will the query SELECT data->>'temp' FROM measurements; return?

medium

A. 22

B. "22"

C. temp

D. Error

Solution

1. Step 1: Understand JSONB operator ->>

   The operator ->> extracts the JSON value as text, so data->>'temp' returns the value of key 'temp' as text.

2. Step 2: Analyze the inserted JSON value

   The value for 'temp' is 22 (a number), extracted as text '22' without quotes in output.

3. Final Answer:

   22 -> Option A

4. Quick Check:

   JSONB ->> extracts text value = 22 [OK]

Hint: ->> extracts JSON value as text [OK]

Common Mistakes:

• Expecting quotes around numbers
• Confusing -> and ->> operators
• Thinking it returns the key name

4. Identify the error in this PostgreSQL table creation: CREATE TABLE users (id INT, preferences jsonb DEFAULT '{}');

medium

A. Default value '{}' is invalid for jsonb type

B. The default '{}' should be cast to jsonb explicitly

C. Missing NOT NULL constraint on id

D. jsonb type cannot have default values

Solution

1. Step 1: Check default value for jsonb column

   PostgreSQL requires default JSON values to be cast explicitly to jsonb type.

2. Step 2: Analyze the given default '{}'

   The '{}' is a string and must be cast as '{}'::jsonb to be valid.

3. Final Answer:

   The default '{}' should be cast to jsonb explicitly -> Option B

4. Quick Check:

   Default JSON values need explicit cast [OK]

Hint: Cast string defaults to jsonb with ::jsonb [OK]

Common Mistakes:

• Assuming '{}' alone is valid jsonb default
• Ignoring type casting for defaults
• Thinking jsonb cannot have defaults

5. You want to store a list of tags for each article in PostgreSQL. Which data type best supports flexible, searchable, and efficient storage of multiple tags?

hard

A. ARRAY of TEXT

B. TEXT

C. JSONB

D. VARCHAR(255)

Solution

1. Step 1: Consider data type features for storing multiple tags

   TEXT stores plain text but not multiple values; VARCHAR limits length; JSONB is flexible but heavier for simple lists.

2. Step 2: Evaluate ARRAY of TEXT for tags

   ARRAY of TEXT stores multiple text values efficiently and supports searching individual tags easily.

3. Final Answer:

   ARRAY of TEXT -> Option A

4. Quick Check:

   ARRAY suits multiple searchable tags best [OK]

Hint: Use ARRAY for multiple simple values [OK]

Common Mistakes:

• Choosing plain TEXT for multiple tags
• Using VARCHAR which limits length
• Overcomplicating with JSONB for simple lists