[SQL] Derived columns / denormalization

2009-01-15 Thread Jamie Tufnell
Hi, I (think I) want to denormalize an aggregate for performance reasons. I think that is the right terminology, please correct me if not. Consider these two tables: items: id serial (pk), group_id int (fk), ... groups: id serial (pk), item_count int -- this is derived from (select

Re: [SQL] Derived columns / denormalization

2009-01-15 Thread Tom Lane
Jamie Tufnell die...@googlemail.com writes: item_count int -- this is derived from (select count(*) from items where group_id = id) ... item_count would be updated by insert/update/delete triggers on the items table, hopefully that would ensure it is always correct? I'm wondering is what