Error:
#1273 – Unknown collation: ‘utf8mb4_unicode_ci’
Reason:
Importing a database exported from new SQL server to and old SQL server.
Best Solution:
Upgrading SQL server is the best solution.
Alternative Solution:
If you don’t have control over hosting, so:
From phpMyAdmin
1) Click the “Export” tab for the database
2) Click the “Custom” radio button
3) Go the section titled “Format-specific options” and change the dropdown for “Database system or older MySQL server to maximize output compatibility with:” from NONE to MYSQL40.
4) Scroll to the bottom and click “GO”.
Another Solution:
Change “utf8mb4_unicode_ci” to “utf8_unicode_ci” but may cause issue in content encoding.
Cheers!