Done.
Thand you very much!
Zhigang
_
From: Jesper Wisborg Krogh [mailto:my...@wisborg.dk]
Sent: Wednesday, February 12, 2014 5:30 PM
To: Morgan Tocker; Zhigang Zhang
Cc: mysql@lists.mysql.com
Subject: Re: LIKE sql optimization
On 12/02/2014 13:16, Morgan Tocker wrote:
Hi
On 12/02/2014 13:16, Morgan Tocker wrote:
> Hi Zhigang,
>
> On Feb 11, 2014, at 8:48 PM, Zhigang Zhang wrote:
>
>> I want to know the reason, in my opinion, to scan the smaller index data has
>> better performance than to scan the whole table data.
> I think I understand the question - you are as
Thank you very much!
Zhigang
-Original Message-
From: Morgan Tocker [mailto:morgan.toc...@oracle.com]
Sent: Wednesday, February 12, 2014 10:16 AM
To: Zhigang Zhang
Cc: mysql@lists.mysql.com
Subject: Re: LIKE sql optimization
Hi Zhigang,
On Feb 11, 2014, at 8:48 PM
Hi Zhigang,
On Feb 11, 2014, at 8:48 PM, Zhigang Zhang wrote:
> I want to know the reason, in my opinion, to scan the smaller index data has
> better performance than to scan the whole table data.
I think I understand the question - you are asking why MySQL will not index
scan, find matching
I checked a myisam table index, the index is a copy of the whole field.
Zhigang
-Original Message-
From: Reindl Harald [mailto:h.rei...@thelounge.net]
Sent: Wednesday, February 12, 2014 10:02 AM
To: mysql@lists.mysql.com
Subject: Re: LIKE sql optimization
because a index
smaller index data
>> > has
>> > better performance than to scan the whole table data.
>> >
>> >
>> >
>> >
>> >
>> > zhigang
>> >
>> >
>> >
>> > _
>> >
>> > From: Mathieu Desharnais [mai
ailto:mdesharn...@diffusion.cc]
> > Sent: Wednesday, February 12, 2014 9:41 AM
> > To: Zhigang Zhang; mysql@lists.mysql.com
> > Subject: Re: LIKE sql optimization
> >
> >
> >
> > Sql database doesn't use index in like statement if it starts with % .
data has
> better performance than to scan the whole table data.
>
> From: Mathieu Desharnais [mailto:mdesharn...@diffusion.cc]
> Sent: Wednesday, February 12, 2014 9:41 AM
> To: Zhigang Zhang; mysql@lists.mysql.com
> Subject: Re: LIKE sql optimization
>
> Sql database doe
t; _
>
> From: Mathieu Desharnais [mailto:mdesharn...@diffusion.cc]
> Sent: Wednesday, February 12, 2014 9:41 AM
> To: Zhigang Zhang; mysql@lists.mysql.com
> Subject: Re: LIKE sql optimization
>
>
>
> Sql database doesn't use index in like statement if it start
@lists.mysql.com
Subject: Re: LIKE sql optimization
Sql database doesn't use index in like statement if it starts with % ..
like 'abcd%' would work though...
To use an index you can store your value using reverse function and index it
.. then your like would use the index.
2
Sql database doesn't use index in like statement if it starts with % ..
like 'abcd%' would work though...
To use an index you can store your value using reverse function and index
it .. then your like would use the index.
2014-02-11 20:23 GMT-05:00 Zhigang Zhang :
> For example:
>
>
>
> Select
Am 12.02.2014 02:23, schrieb Zhigang Zhang:
> For example:
>
> Select * from T where col like ‘%abcd’;
>
> The table T is myisam table and we created a index on col.
>
> As we known, this like sql does not use the index created on col, it confuse
> me, why?
>
> I think in mysiam engine, the i
For example:
Select * from T where col like ‘%abcd’;
The table T is myisam table and we created a index on col.
As we known, this like sql does not use the index created on col, it confuse
me, why?
I think in mysiam engine, the index data is smaller, it can use index link
list to op
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