Solution for ERROR 1273 (HY000): Unknown collation: utf8mb4_unicode_520_ci

The ERROR 1273 (HY000): Unknown collation message during a MySQL/MariaDB import means the destination server does not recognize a collation referenced by the dump. This is common when a dump is created on a different database engine or a newer/different release.

1. Identify source and destination versions

mysql --version
mysql -e "SELECT VERSION();"

Do not replace the collation blindly before confirming which engine/version produced the export and which one will receive it.

2. Check whether the destination supports the collation

mysql -e "SHOW COLLATION LIKE 'utf8mb4_unicode_520_ci';"

3. If you must replace it

For a migration where the exact UCA 5.2 collation behavior is not required, you can create a copy of the SQL dump and replace unsupported collation declarations with a destination-supported utf8mb4 collation. Keep the original dump unchanged.

cp backup.sql backup-original.sql
sed 's/utf8mb4_unicode_520_ci/utf8mb4_unicode_ci/g' backup-original.sql > backup-compatible.sql

After import, test sorting/comparison behavior for language-sensitive data. Choosing a different collation can affect sort and comparison semantics; it is not merely a cosmetic string replacement.

Better long-term fix

If the application supports it, align source and destination database versions/collation policy as part of the migration plan rather than repeatedly patching dumps.

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