| Lists: | pgsql-sql |
|---|
| From: | T E Schmitz <mailreg(at)numerixtechnology(dot)de> |
|---|---|
| To: | pgsql-sql(at)postgresql(dot)org |
| Subject: | INDEX and LIKE |
| Date: | 2004-11-29 12:19:12 |
| Message-ID: | 41AB13C0.40909@numerixtechnology.de |
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| Lists: | pgsql-sql |
Hello,
I need to be able to perform wildcard searches on a VARCHAR(100) column
of the form
SELECT * FROM item WHERE serial_no LIKE '%12345678%'
Would an index on serial_no do anything at all for this search?
--
Regards/Gruß,
Tarlika Elisabeth Schmitz
| From: | "Olivier Hubaut" <olivier(at)scmbb(dot)ulb(dot)ac(dot)be> |
|---|---|
| To: | pgsql-sql(at)postgresql(dot)org |
| Subject: | Re: INDEX and LIKE |
| Date: | 2004-11-29 13:45:42 |
| Message-ID: | opsh8a6gzu94ope3@olivier.amaze.ulb.ac.be |
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| Lists: | pgsql-sql |
On Mon, 29 Nov 2004 12:19:12 +0000, T E Schmitz
<mailreg(at)numerixtechnology(dot)de> wrote:
> Hello,
>
> I need to be able to perform wildcard searches on a VARCHAR(100) column
> of the form
>
> SELECT * FROM item WHERE serial_no LIKE '%12345678%'
>
> Would an index on serial_no do anything at all for this search?
>
No, It wouldn't. If you use "%" for the beginning of you search pattern, a
seqential search is performed, ignoring the index wich use the beginning
of the string in order to create it's B-tree.
--
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