I made a mistake when I made a MariaDB database for a WordPress website.

The website would use Japanese and therefore the database charset should have been set "utf8mb4" as. I, however, did CREATE DATABASE without specific options and so it was "c" instead of "utf8mb4" unfortunately.

I updated its charset and collation with this SQL:

-- accessing through `mysql -u <user> -p`
ALTER DATABASE <database> \
    CHARACTER SET='utf8mb4' \
    COLLATE='utf8mb4_unicode_ci' \
    ;

Well, it is also able to get charsets via SQL:

SELECT SCHEMA_NAME, DEFAULT_CHARACTER_SET_NAME, DEFAULT_COLLATION_NAME \
    FROM information_schema.SCHEMATA;

Reference:

• MariaDB - Setting Character Sets and Collations