Question

Not sure if such functionality exists but I’m curious if I have the following DB as shown below, if it can be updated such that wherever first_name and last_name match all deduction and pay columns are added together, and thus a single line formed. I know a query can be written to get me such information, but I need this query result to actually become the database. (i.e. cleaning superfluous extra lines sort to speak).

i.e.

first_name | last_name | deduction | pay
skywalker  | luke      | 100       | 200 
vader      | darth     |  50       | 100 
skywalker  | luke      | 400       | 500

becomes

first_name | last_name | deduction | pay
skywalker  | luke      | 500       | 700 
vader      | darth     |  50       | 100 

Thanks for the help/advice!

Answer 1

Answer 1

Create a trigger and another table

You could create a table called star_wars and another called star_wars_roll_up. Then a trigger on star_wars that aggregate data to star_wars_roll_up. You write to star_wars and read from star_wars_roll_up. It is safe to delete anything from star_wars whenever you feel like it.

create table star_wars (name varchar(100), deduction int, pay int);
create table star_wars_roll_up (name varchar(100), deduction int, pay int, primary key (name));
delimiter //
create trigger roll_up before insert on star_wars for each row begin insert into star_wars_roll_up values (new.name, new.deduction, new.pay) on duplicate key update deduction = deduction + new.deduction, pay = pay + new.pay;
end //
delimiter ;

insert into star_wars values ('luke', 100, 100);
insert into star_wars values ('luke', 100, 100);
insert into star_wars values ('luke', 100, 100);
select * from star_wars; select * from star_wars_roll_up;