Illegal mix of collations (utf8mb4_unicode_ci,IMPLICIT) and (utf8mb4_general_ci,IMPLICIT) for operation '='

Check connection with charset=utf8mb4

'dsn'       => 'mysql:dbname=DatabaseName;host=localhost;charset=utf8mb4';

After many hours i finally found a solution that worked for me (using phpMyAdmin).

Remember to first backup your database before performing these operations.

1. Log into phpMyAdmin.
2. Select your database from the list on the left.
3. Click on "Operations" from the top set of tabs.
4. In the Collation box (near the bottom of the page), choose your new collation from the dropdown menu.

I also checked
*Change all tables collations
*Change all tables columns collations

I don't think its 100% necessary, but its also a good idea to restart your mySQL/MariaDb service + Disconnect and reconnect to the database.

Additional note: I had to use utf8mb4_general_ci because the issue persisted when using utf8mb4_unicode_ci (which i originally wanted to use)

For additional information, command line queries and illustrated examples i recommend this article: https://mediatemple.net/community/products/dv/204403914/default-mysql-character-set-and-collation

Had the same problem and fixed it by updating the field's collation.

Even if you change the table's collation, the individual table fields still have the old collation. Try to alter the table and update those varchar fields

See example here

-- This worked for me

SET collation_connection = 'utf8mb4_general_ci';
ALTER DATABASE your_bd CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci;
ALTER TABLE your_table CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci;

First, check your collation of table and database, make it similar if they are different.

If you are getting error in stored procedure, than first check the Collations of your DB and the column on which you are making equal operation, if they are different change the column collate to whatever is your DB and then you have to re-create that stored procedure by dropping it.

The issue is both tables have the same column, to overcome this issue we need to ALTER both the tables and database

ALTER DATABASE databasename CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;

ALTER TABLE tabel1 CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;

ALTER TABLE tabel2 CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;