When a higher version of mysql, such as mysql8, the exported sql file

is imported into a lower version of mysql

If the utf8mb4 character set is used, this error will occur

ERROR 1273 (HY000) at line 199: Unknown collation: ‘utf8mb4_0900_ai_ci’

The solution is to replace the utf8mb4_0900_ai_ci with utf8mb4_general_ci in the sql file in bulk