create table a ( id serial primary key, ... -- some more fields not relevant for my question ); create table b ( id serial primary key, ... -- some more fields not relevant for my question ); create table a_b ( a int not null references a, b int not null references b );
Tables a and b have already been filled with lots of rows. Now my application needs to insert the relationship of a to b into table a_b and is currently doing it with inserts like the following:
insert into a_b(a,b) values(1,100); insert into a_b(a,b) values(1,200); insert into a_b(a,b) values(1,54); insert into a_b(a,b) values(1,4577);
So for a batch of inserts the value of a stays the same, while for by arbitrary values are inserted. Now I have wondered if PostreSQL offers a smarter way to insert those values? A solution can contains usage of some plpgsql code.
It depends on your logic. If you can write a query that selects out the a and b records, there is a smart way:
insert into a_b(a, b)
select 1, b.id from b where b.id in (100, 200, 54, 4577);
This is not really smart because you already have the id values - the select may diminish your performance rather than help. But if the select is "smarter" then you don't even need to know what the b.id values are:
insert into a_b(a, b)
select 1, b.id from b where b.somecolumn = 'somevalue';
Hope this helps.
================================================================== Aaron Bono Aranya Software Technologies, Inc. http://www.aranya.com http://codeelixir.com ==================================================================