Mysql multi-table query 1267 error report

const books = await mysql("books")
                  .select("books.*","csessioninfo.user_info")
                  .join("csessioninfo","books.openid","csessioninfo.open_id")
                  // .orderBy("id","desc")

 code: "ER_CANT_AGGREGATE_2COLLATIONS", errno: 1267, sqlMessage: "Illegal mix of collations (utf8mb4_0900_ai_ci,IMPLICIT) and (utf8mb4_unicode_ci,IMPLICIT) for operation \"=\"", sqlState: "HY000", index: 0, sql: "select `books`.*, `csessioninfo`.`user_info` from `books` inner join `csessioninfo` on `books`.`openid` = `csessioninfo`.`open_id`" } +1ms

execute the above code with an error of 1267. I don"t know what caused it.


mysql> select `books`.*, `csessioninfo`.`user_info` from `books` inner join `csessioninfo` on `books`.`openid` = `csessioninfo`.`open_id`
    -> ;
ERROR 1267 (HY000): Illegal mix of collations (utf8mb4_0900_ai_ci,IMPLICIT) and (utf8mb4_unicode_ci,IMPLICIT) for operation "="