MySQL raises EE_UNKNOWN_COLLATION when a query references a collation that is neither compiled into the server nor listed in the configured character-sets directory.
MySQL Error 28 EE_UNKNOWN_COLLATION appears when a query, table, or server setting refers to an unknown collation. Replace or install the missing collation or upgrade to a server build that supports it to resolve the issue.
Collation '%s' is not a compiled collation and is not specified in the '%s' file
The exact message is: Collation '%s' is not a compiled collation and is not specified in the '%s' file. MySQL throws this global error at parse time when it encounters an unrecognized collation identifier.
The server expects the requested collation to be either compiled into the binary or declared in the Index.xml inside its share/charsets directory.
If neither is true, the lookup fails and error 28 is returned.
The error surfaces during CREATE TABLE, ALTER TABLE, SET NAMES, or connection negotiation whenever a non-existent collation name or ID is sent to the server.
It also appears after restoring dumps created on a newer MySQL version with collations unknown to the target server.
Queries that reference an invalid collation cannot execute, blocking schema migrations, data imports, and even new client connections. Production outages may follow if applications rely on those operations. Addressing the root cause prevents cascading failures and data corruption.
.
Typos such as utf8m4_unicode_ci instead of utf8mb4_unicode_ci are the most frequent trigger.
A dump taken from MySQL 8.0 that uses utf8mb4_0900_ai_ci will fail on a 5.7 server that lacks that collation.
When --character-sets-dir points to an empty or incorrect path, MySQL cannot load external collation files.
A client driver may request an unsupported collation during the handshake, triggering the error before a query is sent.
.
It originates inside the MySQL server, but client drivers can trigger it during handshake by asking for an unsupported collation.
No. MySQL rejects the entire statement. You must supply a valid collation or alter the server's charsets directory.
Upgrading usually helps if the collation exists in newer builds. Verify with SHOW COLLATION before migrating.
Galaxy's schema-aware autocomplete lists only valid collations for your connected server, reducing typos and mismatched versions.
.avif)
.avif){kind=logo}
