On Mittwoch 25 Februar 2009 Tony Liao wrote:
> hi all,
> I have a table table_A (id serial,prefix varchar),for example.
> now I want to get the id of "johnsmith"'s prefix match
> table_A.prefix,so I do select id from table_A where 'johnsmith' like
> prefix||'%'
SELECT id FROM table_A WHERE prefix LIKE 'johnsmith%';
> ,the table_A is very large so I would like to make
> index. create table_A_index on table_A(prefix)
> I try to explain analyze,but it doesn't work ,it use seq scan.
Because your SELECT was wrong.
> I try another index. drop index table_A_index; create
> table_A_index on table_A(prefix varchar_pattern_ops); it doesn't
> work,too.
> thanks
> ps:I have another table table_B would use table_B.prefix=
> table_A.prefix.so how can I create the index?
That's a foreign key, if I understand you correctly.
ALTER TABLE ONLY B
ADD CONSTRAINT B_prefix_fkey FOREIGN KEY (prefix) REFERENCES
A(prefix) ON UPDATE CASCADE ON DELETE CASCADE;
mfg zmi
--
// Michael Monnerie, Ing.BSc ----- http://it-management.at
// Tel: 0660 / 415 65 31 .network.your.ideas.
// PGP Key: "curl -s http://zmi.at/zmi.asc | gpg --import"
// Fingerprint: AC19 F9D5 36ED CD8A EF38 500E CE14 91F7 1C12 09B4
// Keyserver: wwwkeys.eu.pgp.net Key-ID: 1C1209B4
--
Sent via pgsql-admin mailing list (pgsql-admin@xxxxxxxxxxxxxx)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-admin
