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ru.cgi.perl
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From : Sergey Tkachuk 2:5040/33.50 20 Aug 2001 16:37:00
To : Pavel Ammosov
Subject : Re: вопрос один по MySQL
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20 Авг 01 08:09, you wrote to me:
PA>>> like давить, like приводит к полному перебору всей таблицы
ST>> Если поле проиндексировано, то LIKE 'some%' будет этот индекс
ST>> использовать.
PA> Hа mysql?
А откуда сомнения?
=================== Cut ===================
*MySQL* also uses indexes for `LIKE' comparisons if the argument to
`LIKE' is a constant string that doesn't start with a wildcard
character. For example, the following `SELECT' statements use indexes:
mysql> select * from tbl_name where key_col LIKE "Patrick%";
mysql> select * from tbl_name where key_col LIKE "Pat%_ck%";
In the first statement, only rows with `"Patrick" <= key_col <
"Patricl"' are considered. In the second statement, only rows with
`"Pat" <= key_col < "Pau"' are considered.
The following `SELECT' statements will not use indexes:
mysql> select * from tbl_name where key_col LIKE "%Patrick%";
mysql> select * from tbl_name where key_col LIKE other_col;
In the first statement, the `LIKE' value begins with a wildcard
character. In the second statement, the `LIKE' value is not a constant.
================= End cut =================
PA> И давно?
Hе знаю. Hо думаю, что да.
Homer
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