Обсуждение: INDEX and LIKE

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INDEX and LIKE

От
T E Schmitz
Дата:
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

Re: INDEX and LIKE

От
"Olivier Hubaut"
Дата:
On Mon, 29 Nov 2004 12:19:12 +0000, T E Schmitz  
<mailreg@numerixtechnology.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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