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==操作符专门用来比较值是否相等 int a=10; int b=10; 则 a==b, 返回 true. 但是, String a = new String("foo"); String b = new String("foo"); a == b, 返回的是 false, 因为 a 和 b 分别是 阅读全文
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19.1 Overview of Optimizer Hints A hint is an instruction to the optimizer. In a test or development environments, hints are useful for testing ... 阅读全文
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16.1 Introduction to SQL Tuning Identifying high load or top SQL statements that are responsible for a large share of the application workload and ... 阅读全文
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do not build indexes unless necessary. 索引是非常占资源的To maintain optimal performance, drop indexes that an application is not using. 不用的索引可以drop掉, 通过toad可以... 阅读全文