On 12/02/2014 13:16, Morgan Tocker wrote:
Hi Zhigang,
On Feb 11, 2014, at 8:48 PM, Zhigang Zhang zzgang2...@gmail.com 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
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
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 index data
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 zzgang2...@gmail.com:
For
@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.
2014-02-11 20:23
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 starts with % ..
like 'abcd%' would work though...
To use an index you
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 doesn't use index in like statement
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.
2014
: 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 starts with % ..
like 'abcd%' would work though
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
Hi Zhigang,
On Feb 11, 2014, at 8:48 PM, Zhigang Zhang zzgang2...@gmail.com 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
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
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