How to change collation in MySql

For each database:

ALTER DATABASE
    database_name
    CHARACTER SET = utf8mb4
    COLLATE = utf8mb4_unicode_ci;

For each table:

ALTER TABLE
    table_name
    CONVERT TO CHARACTER SET utf8mb4
    COLLATE utf8mb4_unicode_ci;

For each column:

ALTER TABLE
    table_name
    CHANGE column_name column_name
    VARCHAR(191)
    CHARACTER SET utf8mb4
    COLLATE utf8mb4_unicode_ci;