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Sorry it’s my mistake, I understood that in this way regulate the number of characters allowed to subscribe to field without any intervention in mysql.

However, there is any way to define the MAX or MIN of the desired character without any intervention in mysql?

I dont understand the second statement. Can you explain further with your use case.

When I add or edit a field I want to define how many characters I can put (eg 50 characters).
Do not allow to subscribe the 51st character.
That I mean, is there any idea?

You can use html maxlength input attribute. HTML engine will not allow 51th input by this.

$col["editoptions"]["maxlength"] = 50;