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51la

转一篇quest Xpert for PL/SQL 的-------Avoid COUNT(*) Unless Count is Required

之前,我还真没想过用rownum来提高性能。至于用游标循环,倒是很简单。Avoid COUNT(*) Unless Count is RequiredConsider the following requirement:Get the ID for the company which matches specified name.If no match, display error.If more than one match, show list.If single match, [...]

今天才听说MapReduce

什么是MapReduce? Google的分布运算开发工具MapReduce,用于大规模数据集(大于1TB)的并行运算! [...]