Monthly Archives: August 2013

Remove Duplicate Rows in MySQL

Duplicate elimination is necessary when the database is messed up or when we integrate data from multiple sources. This tutorial shows several ways of removing duplicates in MySQL that may fit in different application scenarios. Suppose we have a table

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Posted in MySQL

Regular Expressions in Java

Regular Expression Basics Regular expressions (regex) are an effective way of describing common patterns in strings. For example, all phone numbers in North America have 10 digits; this can be easily described by regular expressions: [0-9]{10}, which matches with 10

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Posted in Java

Pseudorandom Generators and Derandomization

Definition of Pseudorandom Generators Two distributions \(X\) and \(Y\) over \(\{0,1\}^n\) are \((s, \epsilon)\)-indistinguishable if, for any circuit \(C\) of size at most \(s\), \[ \left| \Pr_X[C(X) = 1] – \Pr_Y[C(Y) = 1] \right| \leq \epsilon. \] A pseudorandom generator

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Posted in Theory