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POOptimize the speed on performing "select" query in a big loop
 

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    <p>I'm performing a simple 'select' query in a Java loop as what is shown below. The size of the List can grow up to 10000+. How can I improve the query speed? Any example or advice is appreciated. Thanks. </p> <p>Do note that I need to retrieve all data in every column of that table, so that's why the asterisk (*) is used.</p> <pre><code>List&lt;String&gt; valueList = .... Connection conn = null; PreparedStatement ps = null; ResultSet rs = null; try { DriverManager.registerDriver(new oracle.jdbc.OracleDriver()); conn = DriverManager.getConnection(dbURL, dbUsername, dbPassword); for (int m = 0; m &lt; valueList.size() ; m++) { String sql = "SELECT * FROM WORKSHEET WHERE " + sheetId + " = '" + valueList.get(m) + "'"; ps = conn.prepareStatement(sql); rs = ps.executeQuery(); // retreive data.... } } </code></pre> <p>Edit: At the end, there are a few ways to speed this query up. I'm using the second way as it prevent ORA-04031 error in future.</p> <ol> <li>Use parameterized 'SELECT' query with 'IN' clause. </li> <li>Create a Nested table and cast array/list of items that comes from JDBC to the created Nested table. </li> <li>Create a temporary table and insert the list of items. Then perform a JOIN to the main table (1 query) and get the results.</li> </ol>
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    1. USWilts C
    1. USWilts C
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    1. CO[SQL Injection Hooooorrrrraaay!](http://bobby-tables.com/) *Sidenote:* Using parameterized queries would also give you a better performance.
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      1. USBobby
    2. COYou've given a reason for the * - any reason you're not using a parameterized query?
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      1. USJon Skeet
    3. COReducing the total number of queries executed by retreiving multiple sheetID/m pairs in each query (`WHERE pair1 or pair2 or pair3 etc...`) would reduce some of the overhead.
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      1. USMarc B
 

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