MySQL dynamically modifies the varchar Length

Although this situation should not happen, we should have designed it in advance and won't be able to change it in the future, but due to the negligence of our previous work, to be honest, it is not only my personal negligence, but also the communication reasons. Of course, the database is designed by me after all. Therefore, I should criticize myself.

Let's talk about the situation: the MySQL field has a varchar value field set too short, set 30 (I vaguely remember that varchar is scalable, of course, the reality does not allow me to vaguely), so I can only find one way to dynamically modify the length of the varchar field while keeping the database data unchanged, finally let me find it.

Alter table name modify column field name varchar (Quantity );

This feature is still quite powerful, but we still remind you not to have this problem during the best design.