mysql version: 8.0
Character set: utf8mb4
Storage engine: innodb
0. The maximum length of a single line is 16382 characters and 65535 bytes (the maximum sum of all fields is 65535)
One, the maximum length of varchar
(1) Maximum length of non-primary key
https://blog.csdn.net/weixin_39622587/article/details/113458448
15936
(2) The maximum length of the primary key
https://blog.csdn.net/weixin_39372979/article/details/80825606
768
--Old upper limit 191