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    <p>You should add an index on <code>(tried, id)</code>.</p> <p>You already added an index on <code>(username,id,tried)</code> but this index cannot be used efficiently for the query you wrote because the field <code>tried</code> is not the first item in the index.</p> <hr> <p>From the manual page <a href="http://dev.mysql.com/doc/refman/5.0/en/mysql-indexes.html" rel="nofollow">How MySQL Uses Indexes</a>:</p> <blockquote> <p>MySQL uses indexes for these operations:</p> <ul> <li><p>To find the <code>MIN()</code> or <code>MAX()</code> value for a specific indexed column <code>key_col</code>. This is optimized by a preprocessor that checks whether you are using <code>WHERE key_part_N = constant</code> on all key parts that occur before <code>key_col</code> in the index. In this case, MySQL does a single key lookup for each <code>MIN()</code> or <code>MAX()</code> expression and replaces it with a constant. If all expressions are replaced with constants, the query returns at once. For example:</p> <p>SELECT MIN(key_part2),MAX(key_part2) FROM tbl_name WHERE key_part1=10;</p></li> </ul> </blockquote> <p>Note in particular that the <code>WHERE</code> clause must refer to columns that occur <em>before</em> the column for which you wish to calculate the <code>MIN</code> or <code>MAX</code>, which is why your current index is not used efficiently.</p> <hr> <blockquote> <p>I need to rapidly do select queries on it in a loop</p> </blockquote> <p>Are you sure that you need to query in a loop? Have you considered moving the loop into the database? Maybe what you really need is a join? It's better to send a single query that fetches a lot of data than lots of small queries that fetch only a small amount of data each.</p>
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    1. POMySQL How can I speed up this SELECT query?
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    1. COi just added the output of show index to my post. Can you please take a look to see if anything looks wrong? also, you're suggesting a create a second compound index right?
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    2. COyes indexing is best option for improving and speed up operation in mysql qureies.
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    3. CO@xendi: You didn't say what the other index is for.
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