Trigger before update a fields in a table I want to know how can I code a trigger that verify a fields before updating it. For example I want to prevent a date update, let say, not to modify records with date before '2020-01-01'.

Thanks in advance.
The answer will vary depending upon the RDBMS you are using. Also DBAs &amp; developers have different preferences.

Personally i would choose to apply this in a stored procedure rather than a trigger. Triggers dont scale well and can give unpredictable results with bulk updates.