postgres=# create table dwache (kaufdatum date, dauer interval, ablauf_garantie date);
CREATE TABLE
postgres=# insert into dwache (kaufdatum , dauer) values (current_date, '1 day');
INSERT 0 1
postgres=# insert into dwache (kaufdatum , dauer) values (current_date, '10 day');
INSERT 0 1
postgres=# insert into dwache (kaufdatum , dauer) values (current_date, '100 day');
INSERT 0 1
postgres=# insert into dwache (kaufdatum , dauer) values (current_date, '1000 day');
INSERT 0 1
postgres=# select * from dwache ;
kaufdatum | dauer | ablauf_garantie
------------+-----------+-----------------
2023-06-05 | 1 day |
2023-06-05 | 10 days |
2023-06-05 | 100 days |
2023-06-05 | 1000 days |
(4 rows)
postgres=# update dwache set ablauf_garantie = kaufdatum + dauer;
UPDATE 4
postgres=# select * from dwache ;
kaufdatum | dauer | ablauf_garantie
------------+-----------+-----------------
2023-06-05 | 1 day | 2023-06-06
2023-06-05 | 10 days | 2023-06-15
2023-06-05 | 100 days | 2023-09-13
2023-06-05 | 1000 days | 2026-03-01
(4 rows)
postgres=#