Re: need help with import

On Thursday 16 Feb 2012, Andreas wrote:
> Hi
> I get CSV files to import.
> Th structure is like this.
> main part, sub part
> Could be like this
>
> A, a1
> A, a2
> A, a3
> B, b1
> B, b2
>
> The database has a table for main_part and one for sub_part.
> The relation needs to be n:m so there is a relation table that holds
> ( main_id, sub_id ).
> The 2 primary keys main_part.id and sub_part.id are both serials.
>
> Is there a way to do an import with SQL?
>
> I can read the CSV into a temporary table
> and I can do a
> INSERT INTO main_part ( ... ) SELECT DISTINCT main columns FROM
> import; as well as a
> INSERT INTO sub_part ( ... ) SELECT sub columns FROM import;
>
> But how would I know what main_id and sub_id to insert into the n:m
> relation?

Is this what you need?

foo=> create table mp(mid serial primary key, m text);
CREATE TABLE
foo=> create table sp(sid serial primary key, s text);
CREATE TABLE
foo=> create table ms(mid int references mp, sid int references sp,
primary key(mid, sid));
CREATE TABLE
foo=> create temporary table t(m text, s text);
CREATE TABLE
foo=> \copy t from '/tmp/x' csv
foo=> select * from t;
m | s
---+----
A | a1
A | a2
A | a3
B | b1
B | b2
(5 rows)

foo=> insert into mp(m) (select distinct m from t);
INSERT 0 2
foo=> insert into sp(s) (select distinct s from t);
INSERT 0 5
foo=> select * from mp;
mid | m
-----+---
1 | A
2 | B
(2 rows)

foo=> select * from sp;
sid | s
-----+----
1 | a1
2 | a2
3 | a3
4 | b1
5 | b2
(5 rows)

foo=> insert into ms (select mid, sid from mp, sp where (m,s) in (select
m, s from t));
INSERT 0 5
foo=> select * from ms;
mid | sid
-----+-----
1 | 1
1 | 2
1 | 3
2 | 4
2 | 5
(5 rows)

foo=>

Regards,

-- Raj
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