Integer types (smallint, integer, bigint) in PostgreSQL - Mini Project: Build & Apply

Working with Integer Types in PostgreSQL

📖 Scenario: You are creating a simple database table to store information about employees in a company. Each employee has an ID number, their age, and their salary in whole dollars.Different integer types can store different ranges of numbers. You will practice creating a table using smallint, integer, and bigint types to store these values efficiently.

🎯 Goal: Create a PostgreSQL table named employees with three columns: employee_id as smallint, age as integer, and salary as bigint. This will help you understand how to use different integer types for different data sizes.

📋 What You'll Learn

Create a table named employees

Add a column employee_id with type smallint

Add a column age with type integer

Add a column salary with type bigint

💡 Why This Matters

🌍 Real World

Companies often store employee information in databases. Choosing the right integer type helps save space and improves performance.

💼 Career

Database administrators and developers must understand data types to design efficient and reliable database schemas.

1

Create the employees table with employee_id as smallint

Write a SQL statement to create a table called employees with one column named employee_id of type smallint.

PostgreSQL

CREATE TABLE employees (
    employee_id smallint
);
-- Your code here

Hint

Use CREATE TABLE employees (employee_id smallint); to create the table with the correct column and type.

2

Add the age column with type integer

Modify the employees table creation SQL to add a second column named age with type integer after employee_id.

PostgreSQL

CREATE TABLE employees (
    employee_id smallint,
    age integer
);
-- Your code here

Hint

Add age integer as a new column separated by a comma.

3

Add the salary column with type bigint

Extend the employees table creation SQL to include a third column named salary with type bigint after age.

PostgreSQL

CREATE TABLE employees (
    employee_id smallint,
    age integer,
    salary bigint
);
-- Your code here

Hint

Add salary bigint as the last column with a comma before it.

4

Complete the table creation with all three columns

Ensure the full SQL statement creates the employees table with columns employee_id as smallint, age as integer, and salary as bigint.

PostgreSQL

CREATE TABLE employees (
    employee_id smallint,
    age integer,
    salary bigint
);
-- Your code here

Hint

Check that all three columns and their types are included in the table creation statement.

Practice

1. Which PostgreSQL integer type is best suited for storing very large whole numbers?

easy

A. bigint

B. smallint

C. integer

D. decimal

Solution

1. Step 1: Understand integer types and their sizes

   smallint stores small numbers, integer stores medium-sized numbers, and bigint stores very large numbers.

2. Step 2: Identify the type for very large whole numbers

   Since the question asks for very large whole numbers, bigint is the correct choice.

3. Final Answer:

   bigint -> Option A

4. Quick Check:

   Very large whole numbers = bigint [OK]

Hint: Biggest integer type is bigint for very large numbers [OK]

Common Mistakes:

• Confusing smallint with bigint
• Choosing decimal which is for decimals, not integers
• Picking integer which is medium size

2. Which of the following is the correct way to declare a column named age as a 2-byte integer in PostgreSQL?

easy

A. age INT2(2);

B. age INTEGER(2);

C. age BIGINT(2);

D. age SMALLINT;

Solution

1. Step 1: Recall PostgreSQL integer type syntax

   PostgreSQL uses SMALLINT for 2-byte integers. The syntax is simply column_name SMALLINT;.

2. Step 2: Evaluate each option

   age SMALLINT; uses correct syntax. The other options incorrectly use size in parentheses (like INT2(2), INTEGER(2), BIGINT(2)), which is invalid for integer types in PostgreSQL.

3. Final Answer:

   age SMALLINT; -> Option D

4. Quick Check:

   2-byte integer = SMALLINT syntax [OK]

Hint: Use SMALLINT keyword for 2-byte integers, no size in parentheses [OK]

Common Mistakes:

• Adding size in parentheses like INTEGER(2)
• Using BIGINT for small numbers
• Specifying size like INT2(2) for integer types

3. What will be the result of this PostgreSQL query?

CREATE TABLE test_numbers (num SMALLINT); INSERT INTO test_numbers VALUES (40000); SELECT * FROM test_numbers;

medium

A. 40000

B. Error: integer out of range

C. 0

D. NULL

Solution

1. Step 1: Understand SMALLINT range

   SMALLINT can store values from -32768 to 32767 only.

2. Step 2: Check inserted value against range

   40000 is greater than 32767, so inserting it causes an error.

3. Final Answer:

   Error: integer out of range -> Option B

4. Quick Check:

   40000 > SMALLINT max 32767 = error [OK]

Hint: Check value fits type range; else error occurs [OK]

Common Mistakes:

• Assuming value truncates silently
• Expecting 0 or NULL instead of error
• Confusing SMALLINT range with INTEGER

4. You wrote this table definition:

CREATE TABLE sales (id INTEGER, amount SMALLINT);

But when inserting a large amount like 40000, you get an error. How do you fix it?

medium

A. Change amount column type to INTEGER

B. Change id column type to SMALLINT

C. Insert smaller values only

D. Change amount column type to tinyint

Solution

1. Step 1: Identify cause of error

   Amount column is SMALLINT which maxes at 32767, so 40000 is too large.

2. Step 2: Choose appropriate type to hold 40000

   INTEGER can hold values up to 2,147,483,647, so changing amount to INTEGER fixes the error.

3. Final Answer:

   Change amount column type to INTEGER -> Option A

4. Quick Check:

   40000 fits INTEGER but not SMALLINT [OK]

Hint: Use INTEGER for values larger than 32767 [OK]

Common Mistakes:

• Changing unrelated column type
• Trying to insert smaller values only
• Choosing tinyint which is a MySQL type, not PostgreSQL

5. You need to store user IDs that can be very large numbers, possibly exceeding 2 billion. Which PostgreSQL integer type should you choose and why?

hard

A. smallint because it uses less storage

B. integer because it supports up to 2 billion

C. bigint because it supports numbers larger than 2 billion

D. serial because it auto-increments

Solution

1. Step 1: Understand size limits of integer types

   smallint max is 32767, integer max is about 2,147,483,647, bigint supports much larger numbers.

2. Step 2: Match requirement to type

   User IDs may exceed 2 billion, so integer is insufficient. bigint is needed to store larger values.

3. Final Answer:

   bigint because it supports numbers larger than 2 billion -> Option C

4. Quick Check:

   IDs > 2 billion need bigint [OK]

Hint: Use bigint for numbers larger than 2 billion [OK]

Common Mistakes:

• Choosing smallint for large IDs
• Assuming integer supports >2 billion
• Confusing serial with integer size