How Can I Fix Incorrect Character Set and Collation in My MySQL Database?

Resolving MySQL Character Set and Collation Problems

Incorrect character set and collation settings in MySQL can lead to data display issues, especially with non-English characters. This guide provides solutions for fixing these problems.

Correcting Database Collation

To change the character set and collation for an entire database, use this command:

ALTER DATABASE <database_name> CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci;

This updates the settings for all tables and columns within the database.

Adjusting Table Collation

For a specific table, use this command:

ALTER TABLE <table_name> CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci;

This applies the new settings to all columns in the table.

Modifying Column Collation

To alter the collation of an individual column, use the MODIFY clause:

ALTER TABLE <table_name> MODIFY <column_name> VARCHAR(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci;

Understanding Collation Components

The utf8mb4_0900_ai_ci collation is composed of:

• utf8mb4: 4-byte UTF-8 encoding (supports a wider range of characters).
• _0900_: Performance optimization for MySQL 9.0 and later.
• _ai_ci: Case-insensitive and accent-insensitive comparison.

After these changes, characters previously displayed as "???" should now render correctly.

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