How to Fix Character Display Issues in MySQL by Changing Database Character Sets and Collations?

Solve MySQL character display problem: change database character set and collation

Incorrect database collation settings can cause character display problems. If you encounter problems with Chinese and Japanese characters being replaced by question marks, it is most likely due to incorrect collation settings. This guide will teach you how to change the character set and collation of your entire MySQL database.

Change database collation

To change the collation of the entire database, use the following query:

<code class="language-sql">ALTER DATABASE <database_name> CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci;</code>

Change table sorting rules

To change the collation of a specific table, execute the following query:

<code class="language-sql">ALTER TABLE <table_name> CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci;</code>

Change column sorting

To change the collation of a column, use the following query:

<code class="language-sql">ALTER TABLE <table_name> MODIFY <column_name> VARCHAR(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci;</code>

Understanding UTF-8 collation

The "utf8mb4_0900_ai_ci" collation used in the example represents:

• 3 bytes: UTF-8
• 4 bytes: UTF-8MB4 (new version)
• v9.0: 0900 (new version)
• _ai_ci: Case and accent insensitive

Advantages of UTF-8MB4_0900_AI_CI

This collation provides improved:

• Storage efficiency (4 bytes per character)
• Sort performance
• Supports all Unicode characters and emojis

More resources

• The difference between utf8_general_ci and utf8_unicode_ci
• How to change the collation of databases, tables, and columns?

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