Analysis of MySQL error121 & amp; error150

Today, the external keywords are used for writing database scripts. Two types of errors are encountered during the runtime: 121 and 150. I found a solution on Google. They are explained as follows:
Error 121: this is an error where the names of external keywords are repeated. The names of external keywords cannot be repeated even in different tables. Www.2cto.com error 150 contains three types of errors: 1. foreign keys and referenced Foreign keys are of different types. For example, integer and double2. the column to be referenced cannot be found. the character encoding of the table is different from that of the author lilee84.