utf8mb4 vs. ASCII/Latin Charsets: Performance and Best Practices for MySQL/MariaDB

Character Sets and Storage

• In a database, text data is stored using character sets. These sets define how characters (letters, numbers, symbols) are represented digitally using a specific number of bits (0s and 1s) per character.
• ASCII (American Standard Code for Information Interchange) is a basic character set that uses 7 bits per character, covering mostly English letters, numbers, and basic punctuation. This makes it space-efficient for storing data limited to these characters.
• Latin character sets (like ISO-8859-1 or Windows-128) extend ASCII by using 8 bits per character, allowing for accented characters used in Western European languages.

utf8mb4: A Versatile Character Set

• utf8mb4 (UTF-8 Multi-Byte character set version 4) is a more comprehensive character set that can handle a vast range of characters from various languages, including those requiring more than 1 byte per character (e.g., Asian languages, emojis). It's the recommended default for modern databases due to its flexibility.

Performance Considerations

• While ASCII/Latin sets might seem like a space-saving choice for databases storing primarily English text, the performance difference is generally negligible in most modern database systems like MySQL and MariaDB. This is because storage space is often less of a bottleneck compared to other factors like query complexity and hardware limitations.
• In some scenarios, using a more specific character set like ASCII for certain columns (e.g., storing postal codes or IDs) might be a good idea to enforce data integrity and potentially gain minimal storage savings. However, the trade-off is that you lose the flexibility to store other character types in those columns.

Best Practices

• For most database applications, especially those that might need to handle internationalization or emojis in the future, using utf8mb4 is the recommended approach. It provides the most flexibility and future-proofing without significant performance drawbacks.
• If you have very specific use cases with strict data limitations (e.g., storing only postal codes) and storage space is a critical concern, you could consider using a more restricted character set like ASCII for those specific columns. However, carefully weigh the benefits against the potential limitations.

In Summary

• Character sets like ASCII/Latin can be space-efficient for limited character use cases.
• utf8mb4 offers superior flexibility for handling a wider range of characters.
• The performance difference between these sets in modern databases is usually minimal.
• Use utf8mb4 as the default for most database applications.
• Consider using a more restricted set for specific columns only if storage is a crucial factor and data limitations are well-defined.

Creating a Table with utf8mb4:

CREATE TABLE my_table (
  id INT PRIMARY KEY AUTO_INCREMENT,
  name VARCHAR(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci,
  description TEXT CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci
);

This code creates a table named my_table with three columns:

• id: An auto-incrementing integer for unique identification.
• name: A VARCHAR column with a maximum length of 255 characters, explicitly specifying the utf8mb4 character set and utf8mb4_unicode_ci collation (case-insensitive sorting).
• description: A TEXT column for longer descriptions, also using utf8mb4 character set and collation.

Specifying Character Set in a Query:

SET NAMES utf8mb4;  -- Ensure the connection uses utf8mb4

SELECT * FROM my_table
WHERE name LIKE '%äöü%' COLLATE utf8mb4_unicode_ci;

This code performs the following actions:

• SET NAMES utf8mb4;: Sets the character set for the current connection to utf8mb4, ensuring proper handling of characters in the query.
• SELECT * FROM my_table: Selects all columns from the my_table.
• WHERE name LIKE '%äöü%': Filters rows where the name column contains characters like "ä", "ö", or "ü" (umlauts).
• COLLATE utf8mb4_unicode_ci: Specifies the collation for the LIKE comparison, ensuring proper handling of accented characters based on Unicode rules and case-insensitive matching.

Using a More Restricted Character Set:

ALTER TABLE my_table
MODIFY postal_code CHAR(10) CHARACTER SET ascii COLLATE ascii_general_ci;

This code modifies the my_table to add a new column named postal_code:

• ALTER TABLE my_table: Targets the my_table for modification.
• MODIFY: Specifies that we're modifying an existing column.
• postal_code CHAR(10): Defines the new column named postal_code as a CHAR data type with a maximum length of 10 characters.
• CHARACTER SET ascii COLLATE ascii_general_ci: Explicitly sets the character set and collation to ascii for this specific column, assuming postal codes only need basic alphanumeric characters and a case-insensitive comparison.

Server Configuration:

• You can modify the default character set for the MySQL or MariaDB server itself by editing the configuration file (my.cnf on most systems). This setting applies to all database connections unless overridden at the connection or table level. However, exercise caution as changing the server-wide setting might affect existing databases that rely on a specific character set.

phpMyAdmin (Web Interface):

• If you're using phpMyAdmin, a popular web-based administration tool for MySQL and MariaDB, you can manage character sets through its interface. Here's the general workflow:
  • Access the "Databases" section in phpMyAdmin.
  • Select the database you want to modify.
  • Look for an option like "Character Set" or "Collation."
  • Choose the desired character set from a dropdown menu.
  • Apply the changes to update the database character set.

Command-Line Tools:

• MySQL and MariaDB offer command-line tools like mysql or mysqladmin that allow character set management. These tools can be used to:
  • Change the character set for an existing database:

    mysql -u username -p database_name -e "ALTER DATABASE database_name CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;"
    

  • Set the character set for a new table:

    mysql -u username -p -e "CREATE TABLE my_table ( ... ) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;" database_name
    

Application-Level Configuration:

• Some programming languages and database libraries might offer ways to specify the character set when connecting to the database. This allows you to configure the character set on a per-application basis.

Choosing the Right Method

The most suitable method depends on your specific needs and preferences:

• For server-wide defaults, consider modifying the configuration file, but proceed with caution.
• For quick visual management, a web interface like phpMyAdmin can be helpful.
• If you prefer command-line control, MySQL and MariaDB tools provide powerful options.
• For application-specific needs, refer to the documentation of your programming language or database library.