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Oracle取前N条记录方法 Oracle实现SELECT TOP N的方法 - 爬虫/数据库 - 清...
select * from ( select * from tablexxx order by xxx desc ) where rownum <= N
oracle数据库不支持mysql中limit, top功能,但可以通过rownum来限制返回的结果集的行数,rownum并不是用户添加的字段,而是oracle系统自动添加的。
Why Collections.sort uses merge sort instead of quicksort?
We know that quick sort is the fastest sorting algorithm.
1 Answer
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How would you count occurrences of a string (actually a char) within a string?
I am doing something where I realised I wanted to count how many / s I could find in a string, and then it struck me, that there were several ways to do it, but couldn't decide on what the best (or easiest) was.
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What are the applications of binary trees?
I am wondering what the particular applications of binary trees are. Could you give some real examples?
17 Answers
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Best Practices: working with long, multiline strings in PHP?
Note: I'm sorry if this is an extremely simple question but I'm somewhat obsessive compulsive over the formatting of my code.
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Append an object to a list in R in amortized constant time, O(1)?
If I have some R list mylist , you can append an item obj to it like so:
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Create list of single item repeated N times
I want to create a series of lists, all of varying lengths. Each list will contain the same element e , repeated n times (where n = length of the list).
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Multiple simultaneous downloads using Wget?
I'm using wget to download website content, but wget downloads the files one by one.
15 Answers
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Finding three elements in an array whose sum is closest to a given number
Given an array of integers, A 1 , A 2 , ..., A n , including negatives and positives, and another integer S. Now we need to find three different integers in the array, whose sum is closest to the given integer S. If there exists more than one solution, any of them is ok.
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How to implement a queue using two stacks?
Suppose we have two stacks and no other temporary variable.
20 Answers
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