utf8_general_ci vs. utf8_unicode_ci: Which MySQL Collation Should I Choose for Unicode Data?

Understanding the Differences Between utf8_general_ci and utf8_unicode_ci

When designing a MySQL database, the choice of collation for Unicode data is crucial. Among the available options, utf8_general_ci and utf8_unicode_ci stand out as popular choices. However, understanding their distinctions is essential to make an informed decision.

utf8_general_ci: A Flawed Collation

utf8_general_ci, despite its widespread use, is a flawed collation for Unicode data. It applies a simplified set of transformations, including normalization, removal of combining characters, and upper case conversion. Unfortunately, this approach fails to account for the complexities of Unicode casing, leading to incorrect results. For instance, it conflates the lowercase "ß" with "ss", and misinterprets the uppercase "ß" as "SS."

utf8_unicode_ci: The Standard Unicode Collation

In contrast to utf8_general_ci, utf8_unicode_ci employs the Unicode Collation Algorithm (UCA). UCA is designed specifically for Unicode data, providing accurate and comprehensive sorting. It supports letter expansions, ligatures, and other Unicode-specific features. As a result, utf8_unicode_ci correctly handles characters like the German ß (which is sorted near "ss") and the Latin ligature Œ (sorted near "OE").

Advantages of utf8_unicode_ci

Beyond its accuracy, utf8_unicode_ci offers several advantages over utf8_general_ci:

• Enhanced Accuracy: UCA ensures correct sorting for a wide range of scripts, including Cyrillic and other non-Latin characters.
• Expansion Support: utf8_unicode_ci seamlessly incorporates letter expansions and ligatures, providing accurate sorting for complex characters.
• Cross-Language Compatibility: utf8_unicode_ci is well-suited for databases that handle data in multiple languages, ensuring consistent sorting across different character sets.

Considerations

While utf8_unicode_ci is generally superior, it comes with a slight performance overhead. Its more complex collation algorithms can result in slightly slower query execution times compared to utf8_general_ci. However, the benefits of accuracy usually outweigh this performance trade-off.

Conclusion

When it comes to choosing a collation for Unicode data, utf8_unicode_ci is the clear winner. Its adherence to the UCA standards ensures accurate and consistent sorting, making it an essential tool for databases that handle Unicode data. While utf8_general_ci may be tempting due to its slightly faster performance, its flawed collation algorithm makes it a poor choice for Unicode data management.

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