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I have a very simple table that looks like this:

It's called anni_tot and it has a single field called anni. Now, there is another table that looks like this:

It is called people_emp.

Now, I want to insert a new field in the table anni_tot and so my table now looks like this:

The task I need to accomplish is: insert in the table people_emp a copy of all those data that contain the previous year (previous to 2020 which is 2019) and update the field anni. The result should be this:

In red there is what I should get. Basically, when a new year is added in the table anni, I need to make a copy of all the data inside people_emp that have the year = year - 1 and update that field to the current year.

I can do this via php but it's pretty hard to maintain. I am trying to do this using a trigger but I am stucked.

I can do this but my problem is that I do now know how to retrieve the data of the rows inside people_emp. Any idea?