从 Java 中创建 SQL 批量更新

Question

我想更新 mySql 数据库中特定列上的每一行。目前，我对每一行使用 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替代方案可以减少时间和资源消耗（比如批量执行准备好的语句）。更新是通过 Java 代码进行的，因为这是我获取值的地方。我也对在服务器上创建存储过程不感兴趣，因为我没有这样做的权利。

Answer 1

下面是一个示例的链接，该示例使用 Java 的准备语句来执行批量更新。我还提供了该网站的示例以供快速参考。

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
        }
    }
}

Answer 2

如果您使用 MySQL，我相信您的问题的简短答案是“否”。没有什么比这更快的了。

事实上，即使是准备好的陈述也不会给你带来任何好处。也许新版本改变了这一点，但我上次检查（几年前），MySQL 无论如何都只是将准备好的语句转换为常规语句。没有缓存任何内容。