MySQL's utf8 charset only supports 3-byte characters. Use utf8mb4 for full Unicode support.
The utf8 charset in MySQL truncates 4-byte characters (emojis, CJK extensions) causing data loss or errors.
BeforeMerge scans your pull requests against this rule and 3+ others. Get actionable feedback before code ships.
MySQL's utf8 charset is actually utf8mb3 — it only supports characters up to 3 bytes. This means:
SELECT TABLE_SCHEMA, TABLE_NAME, COLUMN_NAME, CHARACTER_SET_NAME
FROM INFORMATION_SCHEMA.COLUMNS
WHERE CHARACTER_SET_NAME = 'utf8'
AND TABLE_SCHEMA NOT IN ('information_schema', 'mysql', 'performance_schema');Or with SQLFluff:
sqlfluff lint --dialect mysql --rules LT01 migration.sql-- Convert a table
ALTER TABLE users CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;
-- Set default for new tables
ALTER DATABASE mydb CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;