When designing a relational database, one common question is: what data type should be used to store a phone number in SQL? Unlike other numerical values, phone numbers come with unique challenges, such as varying lengths, country codes, and formatting differences. Choosing the right data type ensures accuracy, consistency, and flexibility in storing phone numbers.
In this comprehensive guide, we’ll explore the best data types for storing phone numbers in SQL, common mistakes to avoid, and best practices for database design.
Should You Store Phone Numbers as Numbers or Strings?
One of the biggest misconceptions is treating phone numbers as purely numerical data. Unlike other numbers, phone numbers:
✔ May contain special characters (e.g., +, –, (, ), spaces).
✔ Do not require mathematical operations like addition or multiplication.
✔ Have varying lengths depending on country codes.
Verdict: Storing phone numbers as text (e.g., VARCHAR) is the best approach since it preserves formatting and prevents accidental data corruption.
Best SQL Data Types for Phone Numbers
1. VARCHAR (Recommended)
Using VARCHAR (variable-length string) is the best practice for storing phone numbers because it accommodates different formats, including international dialing codes.
Example:
sql
CREATE TABLE contacts (
id INT PRIMARY KEY,
name VARCHAR(100),
phone_number VARCHAR(20) — Allows flexibility for different formats
);
✔ Supports country codes (e.g., +1, +44).
✔ Allows different formats (e.g., 555-123-4567, (555) 123-4567).
✔ Prevents data corruption due to truncation or leading zero removal.
What Length Should You Use?
- VARCHAR(15): Suitable for most local phone numbers.
- VARCHAR(20-25): Recommended for international numbers.
2. CHAR (Fixed-Length Alternative)
If you require a fixed-length phone number format, CHAR is an option.
Example:
sql
CREATE TABLE users (
user_id INT PRIMARY KEY,
phone_number CHAR(15) — Fixed-length for standard formats
);
✔ Ensures uniform data entry.
❌ Wastes space if phone numbers vary in length.
3. BIGINT (Not Recommended)
A common mistake is storing phone numbers as BIGINT (large integer).
sql
CREATE TABLE customers (
customer_id INT PRIMARY KEY,
phone_number BIGINT
);
Why This Is a Bad Idea:
❌ Loses Leading Zeros – A phone number like 0123456789 would be stored as 123456789.
❌ Inflexible – Cannot store + symbols or formatted numbers.
❌ No Arithmetic Operations – You never need to add or multiply phone numbers.
Verdict: Avoid storing phone numbers as numeric types like BIGINT or INT.
Common Mistakes in Storing Phone Numbers
1. Ignoring Country Codes
Phone numbers differ by country, so always account for country codes.
✔ Use VARCHAR(20+) to accommodate + symbols.
✔ Store country codes in a separate column if necessary.
Example:
sql
CREATE TABLE phone_directory (
id INT PRIMARY KEY,
country_code VARCHAR(5),
phone_number VARCHAR(15)
);
2. Storing Raw Numbers Without Formatting
If you store phone numbers as plain digits, they can become unreadable. Consider standardizing formatting for consistency.
✔ Use a separate column for a formatted version of the number.
✔ Apply formatting at the application level (e.g., with Python, JavaScript).
Example:
sql
CREATE TABLE clients (
id INT PRIMARY KEY,
phone_number VARCHAR(20),
formatted_number VARCHAR(25) — Readable format
);
3. Allowing Invalid Data Entry
Without constraints, users may enter incomplete or incorrect phone numbers.
✔ Use CHECK constraints to enforce patterns.
✔ Implement REGEX validation in applications.
Example:
sql
ALTER TABLE contacts ADD CONSTRAINT phone_format
CHECK (phone_number ~ ‘^\+\d{1,3}-\d{3}-\d{3}-\d{4}$’);
✔ Ensures phone numbers follow a standard format.
How to Store and Format Phone Numbers in SQL
1. Storing Phone Numbers in E.164 Format (Recommended)
The E.164 standard is the internationally recognized format for phone numbers.
✔ Format: +[Country Code][Subscriber Number]
✔ Example: +15551234567
Example:
sql
INSERT INTO phone_book (name, phone_number) VALUES
(‘Alice’, ‘+15551234567’),
(‘Bob’, ‘+442071838750’);
2. Storing Phone Numbers in Separate Fields
For better organization, you can split phone numbers into multiple columns.
Example:
sql
CREATE TABLE users (
user_id INT PRIMARY KEY,
country_code VARCHAR(5),
area_code VARCHAR(5),
subscriber_number VARCHAR(15)
);
✔ Allows for better query flexibility.
✔ Useful for applications needing internationalization.
Best Practices for Storing Phone Numbers in SQL
✔ Use VARCHAR(20-25) – Accommodates different formats and country codes.
✔ Follow E.164 Format – Ensures consistency across different systems.
✔ Normalize Data – Store country codes separately if needed.
✔ Apply Constraints – Use regex validation for better data quality.
✔ Handle Formatting at the Application Level – Store raw numbers but format them in user interfaces.
FAQs About SQL Phone Number Data Types
1. What Is the Best SQL Data Type for a Phone Number?
The best data type for storing phone numbers in SQL is VARCHAR(20-25), as it supports different formats, country codes, and special characters.
2. Can I Store Phone Numbers as BIGINT in SQL?
No. BIGINT is not recommended because it removes leading zeros, cannot store + symbols, and does not support varied formatting.
3. What Length Should a Phone Number Column Be in SQL?
- VARCHAR(15): Standard for local numbers.
- VARCHAR(20-25): Recommended for international numbers.
4. Should I Store Country Codes Separately?
Yes. Storing country codes in a separate column improves searchability and allows better formatting.
5. How Can I Enforce a Phone Number Format in SQL?
Use a CHECK constraint with a regex pattern:
sql
ALTER TABLE users ADD CONSTRAINT phone_format
CHECK (phone_number ~ ‘^\+\d{1,3}-\d{3}-\d{3}-\d{4}$’);
Conclusion
Choosing the right data type for storing phone numbers in SQL is crucial for database accuracy and efficiency. While BIGINT and INT should be avoided due to their limitations, using VARCHAR(20-25) is the best approach for handling different phone number formats, including international numbers.
By following best practices such as using E.164 formatting, implementing constraints, and handling formatting at the application level, you can ensure consistent, accurate, and flexible phone number storage in SQL databases.
