问题描述

我想更新 mySql 数据库中特定列的每一行.目前我正在为每一行使用 java.sql.PreparedStatement 并在 for 循环中迭代.我想知道在 Java 编程方面是否还有其他选择可以减少时间和资源消耗(例如批量执行准备好的语句).更新是由 Java 代码进行的，因为这是我从中获取值的地方.我也对在服务器上创建存储过程不感兴趣，因为我没有权限.

I want to update every row on a specific column in a mySql database. Currently I am using a java.sql.PreparedStatement for each row and iterating in a for loop. I was wondering if there were any other alternatives in terms of Java programming to make this less time and resource consuming (something like executing the prepared statements in a batch). The updates are made from Java code because that is where I get the values from. I am also not interested in making stored procedures on the server as I do not have the rights for that.

推荐答案

这是一个使用 Java 的预处理语句来执行批量更新的示例的链接.我还包括了网站上的示例以供快速参考.

Here is a link to an example that uses Java's prepared statement to execute a batch update. I also included the sample from the site for quick reference.

http://www.exampledepot.com/egs/java.sql/BatchUpdate.html

try {
    // Disable auto-commit
    connection.setAutoCommit(false);

    // Create a prepared statement
    String sql = "INSERT INTO my_table VALUES(?)";
    PreparedStatement pstmt = connection.prepareStatement(sql);

    // Insert 10 rows of data
    for (int i=0; i<10; i++) {
        pstmt.setString(1, ""+i);
        pstmt.addBatch();
    }

    // Execute the batch
    int [] updateCounts = pstmt.executeBatch();

    // All statements were successfully executed.
    // updateCounts contains one element for each batched statement.
    // updateCounts[i] contains the number of rows affected by that statement.
    processUpdateCounts(updateCounts);

    // Since there were no errors, commit
    connection.commit();
} catch (BatchUpdateException e) {
    // Not all of the statements were successfully executed
    int[] updateCounts = e.getUpdateCounts();

    // Some databases will continue to execute after one fails.
    // If so, updateCounts.length will equal the number of batched statements.
    // If not, updateCounts.length will equal the number of successfully executed statements
    processUpdateCounts(updateCounts);

    // Either commit the successfully executed statements or rollback the entire batch
    connection.rollback();
} catch (SQLException e) {
}

public static void processUpdateCounts(int[] updateCounts) {
    for (int i=0; i<updateCounts.length; i++) {
        if (updateCounts[i] >= 0) {
            // Successfully executed; the number represents number of affected rows
        } else if (updateCounts[i] == Statement.SUCCESS_NO_INFO) {
            // Successfully executed; number of affected rows not available
        } else if (updateCounts[i] == Statement.EXECUTE_FAILED) {
            // Failed to execute
        }
    }
}

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