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Turning a subselect into an array

P: n/a
I'm sure this has been answered before, but the search seems to be down
again.

How can I convert the results of a subselect into an array? IE:

CREATE TABLE a(a int, b int, c int[]);
INSERT INTO table_a
SELECT a, b, (SELECT c FROM table_c WHERE table_c.parent = table_b.id)
FROM table_b
;
--
Jim C. Nasby, Database Consultant de*****@decibel.org
Give your computer some brain candy! www.distributed.net Team #1828

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Nov 23 '05 #1
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3 Replies


P: n/a
On Thu, Oct 28, 2004 at 05:37:29PM -0500, Jim C. Nasby wrote:
I'm sure this has been answered before, but the search seems to be down
again.

How can I convert the results of a subselect into an array? IE:

CREATE TABLE a(a int, b int, c int[]);
INSERT INTO table_a
SELECT a, b, (SELECT c FROM table_c WHERE table_c.parent = table_b.id)
FROM table_b


See the "Array Constructors" section in the PostgreSQL documentation:

http://www.postgresql.org/docs/7.4/s...Y-CONSTRUCTORS

INSERT INTO table_a
SELECT a, b, ARRAY(SELECT c FROM table_c WHERE table_c.parent = table_b.id)
FROM table_b

--
Michael Fuhr
http://www.fuhr.org/~mfuhr/

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Nov 23 '05 #2

P: n/a
Ok, next stupid question that I can't find in the docs... How would I
join a table to an array? IE: if I have an array of primary keys for
some table and I want to get the name field from that table and turn it
back into an array, how would I do that?

On Thu, Oct 28, 2004 at 05:21:52PM -0600, Michael Fuhr wrote:
On Thu, Oct 28, 2004 at 05:37:29PM -0500, Jim C. Nasby wrote:
I'm sure this has been answered before, but the search seems to be down
again.

How can I convert the results of a subselect into an array? IE:

CREATE TABLE a(a int, b int, c int[]);
INSERT INTO table_a
SELECT a, b, (SELECT c FROM table_c WHERE table_c.parent = table_b.id)
FROM table_b


See the "Array Constructors" section in the PostgreSQL documentation:

http://www.postgresql.org/docs/7.4/s...Y-CONSTRUCTORS

INSERT INTO table_a
SELECT a, b, ARRAY(SELECT c FROM table_c WHERE table_c.parent = table_b.id)
FROM table_b

--
Michael Fuhr
http://www.fuhr.org/~mfuhr/

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--
Jim C. Nasby, Database Consultant de*****@decibel.org
Give your computer some brain candy! www.distributed.net Team #1828

Windows: "Where do you want to go today?"
Linux: "Where do you want to go tomorrow?"
FreeBSD: "Are you guys coming, or what?"

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Nov 23 '05 #3

P: n/a
On Fri, Oct 29, 2004 at 05:13:02PM -0500, Jim C. Nasby wrote:
Ok, next stupid question that I can't find in the docs... How would I
join a table to an array? IE: if I have an array of primary keys for
some table and I want to get the name field from that table and turn it
back into an array, how would I do that?


See the "Subquery Expressions" and "Row and Array Comparisons"
sections in the PostgreSQL documentation:

http://www.postgresql.org/docs/7.4/s...-subquery.html
http://www.postgresql.org/docs/7.4/s...mparisons.html

If I understand you correctly, this should work:

SELECT ARRAY(SELECT name FROM foo WHERE id = ANY(ARRAY[1,2,3]));

A test I just ran showed "id = ANY(ARRAY[1,2,3])" doing a sequential
scan whereas "id IN (1,2,3)" did an index scan, so you might want to
use the latter if possible.

--
Michael Fuhr
http://www.fuhr.org/~mfuhr/

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Nov 23 '05 #4

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