From: Reindl Harald
Date: February 12 2012 10:40pm
Subject: Re: Indexed Query examining too many rows!
List-Archive: http://lists.mysql.com/mysql/226785
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Am 12.02.2012 23:25, schrieb Cabbar Duzayak:
> Hi All,
>=20
> I have a table with a btree index on its searchKey column, and when I
> send a simple query on this table:
>=20
> explain select * from DataIndex where (searchKey like 'A%') order by
> searchKey limit 10
>=20
> rows is returning 59548 and it tells me that it is using the searchKey =
index.
>=20
> Also, a select count(*) on this table returns 32104 rows, i.e.
>=20
> select count(*) from DataIndex where searchKey like 'a%' -> gives
> 32104 as its result
>=20
> Am I doing something wrong here? Given that the searched column is
> indexed, shouldn't it examine way less rows?

LIKE does not benefit from keys!


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