Database systems like MySQL use different character encodings to efficiently store and process text data. Two of the most commonly used encodings are UTF-8 and UTF8MB4. While they may seem similar at first glance, there are key differences between them that have a significant impact on working with databases and handling international characters.
What is UTF-8?
UTF-8 is one of the most widely used character encodings globally. This format allows the storage of variable-length characters, meaning that characters can be represented using 1 to 4 bytes. Most common characters (such as Latin alphabet letters) are stored using 1 byte, while some special characters may require up to 4 bytes. This format is optimized for texts in the Latin alphabet and has long been the preferred choice in many database systems.
What is UTF8MB4?
On the other hand, UTF8MB4 is an extended version of standard UTF-8 that allows the use of 4 bytes for all characters. While in regular UTF-8, some characters are represented with only three bytes, UTF8MB4 allows full four-byte encoding. This means that this format can store a wide range of characters, including emojis, some older Chinese characters, or special symbols.
Key Differences Between UTF-8 and UTF8MB4
1. Maximum Number of Bytes per Character
- UTF-8: A maximum of 3 bytes per character. This means that some special characters that require 4 bytes cannot be stored in this format.
- UTF8MB4: Allows up to 4 bytes per character. This enables the database to store characters that were not supported in UTF-8.
2. Support for Special Characters
- UTF-8: Does not support all special characters, such as some emojis or older characters used in some languages (e.g., Chinese or Japanese).
- UTF8MB4: Supports all characters, including emojis, special symbols, and the full set of Unicode characters.
3. Compatibility with International Characters
- UTF-8: Is sufficient for many applications that do not use special characters or emojis.
- UTF8MB4: Is ideal for applications that need support for a wide range of characters and symbols. This is especially important for modern applications that often process content from various languages and platforms (e.g., social networks, e-commerce, etc.).
4. Size of Stored Data
- UTF-8: Since common characters (such as the Latin alphabet) are stored using 1 or 2 bytes, this format is less demanding in terms of storage space compared to UTF8MB4.
- UTF8MB4: Since it allows up to 4 bytes per character, the resulting size of stored data can be larger, especially if the application processes a lot of special characters.
Which Format to Choose for a Database?
The choice between UTF-8 and UTF8MB4 depends on the specific use case of the database:
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If the application processes only common text in Latin script or other simple characters, UTF-8 is sufficient and a more efficient choice in terms of storage space.
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If the application processes international characters, emojis, or various special symbols, it is better to use UTF8MB4, even though it may require more storage space.
Changing the Encoding from UTF-8 to UTF8MB4 in MySQL
If you are running a database in MySQL and want to switch from UTF-8 to UTF8MB4, it's important to keep in mind that this transition may require modifications to existing tables and indexes.
For example:
ALTER TABLE table_name CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;
This command will change the table’s encoding to UTF8MB4. It's also important to note that index length in MySQL is limited to 767 bytes, so if you have columns with long text and use them as indexes, it may be necessary to adjust those indexes to comply with the new requirements.
UTF-8 and UTF8MB4 are both very useful character encodings, but each has its specific use case. If you need support for the complete set of Unicode characters, including emojis and special symbols, UTF8MB4 is clearly the better choice. On the other hand, if you're focusing on efficiency and don’t use special characters, UTF-8 may be sufficient.
