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MySQL utf8 vs utf8mb4: What is the Difference Between utf8 and utf8mb4?
When working with MySQL databases, you may encounter the character encodings utf8 and utf8mb4, which might appear similar at first glance. However, they have significant differences that can impact how your data is stored and displayed, especially when dealing with diverse characters and emojis. Understanding the differences between utf8 and utf8mb4 is crucial for choosing the right character set for your database and ensuring that your data is stored correctly.
In this article, we will explore the distinctions between utf8 and utf8mb4 in MySQL, why utf8mb4 was introduced, and how to migrate your database to use utf8mb4 if necessary.
What is utf8 in MySQL?
In MySQL, the utf8 character set was historically used to store Unicode data. It was intended to support all Unicode characters, making it suitable for most text data, including many languages and special characters. However, MySQL’s utf8 implementation only supports a subset of the full UTF-8 standard.
How Many Bytes Does utf8 Use?
MySQL’s utf8 character set encodes characters using 1 to 3 bytes per character. This means that it cannot represent characters that require 4 bytes, such as certain emojis, and some less commonly used Chinese, Japanese, and Korean (CJK) characters. If you try to store such 4-byte characters in a utf8 column, MySQL will return an error, causing data insertion failures.
Example of Unsupported Characters with utf8:
- Emojis like 😊, 🚀, and ❤️.
- Some rare CJK characters.
- Mathematical symbols and other specialized Unicode symbols.
This limitation led to the introduction of utf8mb4 in MySQL.
What is utf8mb4 in MySQL?
The utf8mb4 character set in MySQL is a true implementation of the full UTF-8 standard. It supports 1 to 4 bytes per character, allowing for the complete range of Unicode characters. This includes all of the characters that utf8 supports, as well as the additional 4-byte characters that utf8 does not.
Why Was utf8mb4 Introduced?
MySQL introduced utf8mb4 to address the shortcomings of utf8. With utf8mb4, you can store any valid Unicode character, including emojis, musical notes, mathematical symbols, and the entirety of the CJK character set. This makes utf8mb4 the preferred character set for modern applications that need to support a wide range of text data.
Key Differences Between utf8 and utf8mb4
| Feature | utf8 | utf8mb4 |
|---|---|---|
| Bytes per Character | 1-3 | 1-4 |
| Unicode Coverage | Partial (excludes 4-byte chars) | Full (supports all Unicode) |
| Emoji Support | No | Yes |
| CJK Characters | Most but not all | All |
| Compatibility | Legacy databases | Recommended for new projects |
1. Byte Length
The most significant difference between utf8 and utf8mb4 is the number of bytes they use to store characters. utf8 supports up to 3 bytes, while utf8mb4 supports up to 4 bytes. As a result, utf8mb4 can store a broader range of Unicode characters.
2. Emoji and Special Characters
If you need to store emojis or any special characters that require 4 bytes, utf8mb4 is the only viable option. With utf8, attempting to store a 4-byte character will result in an error, causing potential data loss or failures in applications.
3. Database Compatibility
utf8 was the default character set for many older MySQL installations, making it compatible with legacy systems. However, for new projects and applications that need to support a global audience with diverse character sets, utf8mb4 is now the recommended choice.
Why Use utf8mb4 Instead of utf8?
Given the limitations of utf8, using utf8mb4 is generally a better choice for modern applications. Here are some reasons to prefer utf8mb4:
- Full Unicode Support: utf8mb4 allows you to store all Unicode characters, including emojis, which are becoming increasingly common in user-generated content.
- Future-Proofing: As new characters are added to the Unicode standard, utf8mb4 ensures that your database can handle them.
- Global Compatibility: With utf8mb4, you don’t need to worry about character set compatibility for different languages and special symbols.
When Should You Still Use utf8?
There are some scenarios where utf8 might still be considered:
- Storage Space: Since utf8mb4 uses up to 4 bytes per character, it may result in slightly larger database sizes compared to utf8. However, this difference is often negligible for most applications.
- Legacy Systems: If you have an existing application or database that uses utf8 and you do not need to store 4-byte characters, switching may not be necessary.
How to Convert a Database from utf8 to utf8mb4
If you decide to migrate an existing MySQL database from utf8 to utf8mb4, it involves a few steps to ensure a smooth transition. Here is a general guide to convert your database to use utf8mb4.
Step 1: Backup Your Database
Before making any changes, always back up your database to prevent data loss:
mysqldump -u username -p database_name > database_backup.sql
Step 2: Change Character Set and Collation
Run the following SQL commands to change the character set and collation of your database, tables, and columns to utf8mb4:
ALTER DATABASE database_name CHARACTER SET = utf8mb4 COLLATE = utf8mb4_unicode_ci;
For each table, run:
ALTER TABLE table_name CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;
This will change the character set and collation for the specified table and its columns.
Step 3: Update Configuration File
To ensure that new tables and columns use utf8mb4 by default, update your MySQL configuration file (my.cnf or my.ini) with the following settings:
[client]
default-character-set = utf8mb4
[mysql] default-character-set = utf8mb4
[mysqld]
character-set-server = utf8mb4
collation-server = utf8mb4_unicode_ci
Restart MySQL to apply the changes:
sudo service mysql restart
Step 4: Verify the Changes
Check that the character set has been updated successfully:
SHOW VARIABLES LIKE 'character_set%';
SHOW VARIABLES LIKE 'collation%';
The output should display utf8mb4 as the character set for your database.
Conclusion
The choice between utf8 and utf8mb4 in MySQL can significantly affect how your data is stored and what types of characters you can support. While utf8 was commonly used in older MySQL versions, it is limited by its inability to store 4-byte characters like emojis. On the other hand, utf8mb4 offers full Unicode support, making it the recommended option for new databases and applications that need to support diverse characters and symbols.
By using utf8mb4, you ensure that your database is ready for modern text content, including emojis and complex multilingual characters. If you are maintaining an existing utf8 database, consider migrating to utf8mb4 to future-proof your application and avoid potential data storage issues.
With a clear understanding of the differences between utf8 and utf8mb4, you can make an informed decision and ensure that your MySQL databases meet the needs of your application and its users. Happy coding!
