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.
From: Mathieu Desharnais [mailto:mdesharnais@stripped]
Sent: Wednesday, February 12, 2014 9:41 AM
To: Zhigang Zhang; mysql@stripped
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 GMT-05:00 Zhigang Zhang <zzgang2008@stripped>:
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
I think in mysiam engine, the index data is smaller, it can use index link
list to optimize it so as to reduce the disk scan than to the whole table