環境
utf8mb4に変更する
ALTER TABLE posts CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_bin;
utf8に戻す
ALTER TABLE posts CONVERT TO CHARACTER SET utf8 COLLATE utf8_unicode_ci;
ALTER TABLE posts CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_bin;
ALTER TABLE posts CONVERT TO CHARACTER SET utf8 COLLATE utf8_unicode_ci;