(Resolved) Unknown collation: utf8mb4_0900_ai_ci

A collation is a set of rules that defines how to compare and sort character strings in a database server. In this tutorial, we are discussing an error faced during database restoration on another server.

Let’s see the problem and solution to the issue faced recently:

Problem

During the migration of a web application, I got the below error while restoring a database on another server. The collation id may differ based on the MySQL version.

Error message:

Error 1273 (HY000) at line 25 Unknown collation: 'utf8mb4_0900_ai_ci'

See the error screenshot during database restoration.

Here you go with a solution.

Solution

After a little investigation, I found that the MySQL server running on the destination is an older version than the source. So we got that the destination server doesn’t contain the required database collation.

Then we do a little tweak in the backup file to resolve this. Edit the database backup file in text editor and replace “utf8mb4_0900_ai_ci” with “utf8mb4_general_ci” and “CHARSET=utf8mb4” with “CHARSET=utf8“.

Replace the below string:

ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci;

with:

ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_general_ci;

Save your file and restore the database.

The Linux system users can use the sed command to replace text in files directly.

sed -i 's/utf8mb4_0900_ai_ci/utf8_general_ci/g' backup.sql  
sed -i 's/CHARSET=utf8mb4/CHARSET=utf8/g' backup.sql  

That it. after the above changes, the database was successfully restored!

Hope this is solution helped you to resolve “Unknown collation: ‘utf8mb4_0900_ai_ci’” issue.