In v2.1.0 and earlier versions (including all versions of v2.0), the character set of TiDB is UTF-8 by default. But starting from v2.1.1, the default character set has been changed into UTF8MB4.
If you explicitly specify the charset of a newly created table as UTF-8 in v2.1.0 or earlier versions, then you might fail to execute DDL operations after upgrading TiDB to v2.1.1.
To avoid this issue, you need to pay attention to:
Before v2.1.3, TiDB does not support modifying the charset of the column. Therefore, when you execute DDL operations, you need to make sure that the charset of the new column is consistent with that of the original column.
Before v2.1.3, even if the charset of the column is different from that of the table,
show create tabledoes not show the charset of the column. But as shown in the following example, you can view it by obtaining the metadata of the table through the HTTP API.